Some thoughts on family structure and social order I've been considering for quite some time, and I'd like to hear your oppinions and any ideas you can contribute:

Wood Elven Society
In most wood elven communities, all adult members of the clan who have lived through 32 summer solstices are of equal rank when it comes to voting for descisions. In practice almost all position of leadership are held by members of a small group of families, from which chiefs, sub-chiefs, council leaders, and captains are selected. People who show exceptional talent might get the attention and support of members of these highborn families, which greatly improves their chances to get selected for leadership positions, but against the resistance of the highborn its almost impossible. Most communities have an inofficial council of elders, which consists of most of the oldest members of the village who are engaged in the politics of the clan. They care a lot less about social status and being accepted into these groups depends mostly on whether or not its members find ones oppinions agreeable to theirs. When the elders publically declare their stance to an issue, large parts of the clan will fall in behind them.
Since elves can live for over 300 years and show not much difference in age for most of that time, personal relationships are even more unstable and fluid than for other races. Even when people enjoy each others company for over two hundred years and they have the immense fortune that neither falls victim to disease, accident or war, it is still very likely that one of them is several decades if not even a century older than the other. Spending the end of ones life with the same people one grew up with is extremely rare for elves and the most common way to deal with it is to treat an elven life as a number of seperate lives following end on end. It is a common practice among elves to make a clear cut every 60 to 80 years and set out to start a new one, either alone or with one or two other friends who still remain from their last life. Usually this means joining another of the clans villages relatively far away from the recent one, but sometimes elves may join other clans or even take on a new name.
The elven idea of a family is relatively small, consisting of just one or two parents and one to three children. Often they last for only 30 to 40 years until the children have left their parents home. With the potentially very great difference in age between siblings, elven children bond much stronger with the other children of the village who are of similar age. The everyday life of elves is centred on a shared home of families, couples, and individuals that may or may not be related by blood. Very often children who grew up at about the same time also end up sharing their first home after they leave their parents home. Some of these shared homes can last for centuries with some members leaving or dying and new ones joining to replace them, but occasionally smaller ones might disband completely when members feel the urge to start anew somewhere else at the same time. Elves who were born into highborn homes usually share homes with other highborn and the same goes for those born into clansmen families, with relatively few exchange between them. Since homes are owned cummunally and blood relatives often lose touch with each other over the decades and century, there is not much need for rules of inheiritance. As a result, there is no real legal concept of marriage and relationships are much more informal than in other cultures.

Gnome Society
In gnome society, each clan is again divided into numerous Houses or Septs. A house often ranges from some dozens to a few hundred gnomes forming a large extended family. Individual homes are tightly clustered together and have their shared common areas, and in cities carved into rock, they often have a single main gate that connects estate to the streets and roads of the town.
In addition to the clans chief, and the villages sub.chiefs, each house has its own leader who speaks for all the families and individuals under him and has a vote in the town council. While every house has just one vote, the oldest, largest, and wealthiest ones still have most of the power, simply because the smaller houses depend on them and can't afford getting caught between the interests of the larger ones.

Human Society
Humans live in extended families that usually range from 10 to 20 individuals, including freeman servants and lowborn salves. Leadership often passes down from father to son, but there are no written rules on this and leaders might instead chose a nephew or daughter as the person he usually entrusts with taking care of the family in his absence or to fill in for him on important occasions, which is usually enough to establish them as the natural successors once he dies or becomes too old to lead. Effectively the leader of the family owns the land, house, and slaves and employs the families servants. But children can demand to be supported by the families of their parents, so marriage is still a very important legal institution to maintain clear records of genealogy. While children born out of wedlock still can make claims, these can be more easily denied. Unmarried parents are regarded as people of doubious trustworthiness as they are avoiding commiting to clear allegiance to one family or another.
Man who can afford to support larger families can have several wifes, but this is usually confined to highborn men who are the leaders of their family and even in the most richest and powerful chieftains more than 4 or 5 is regarded as highly decadent and a sign of poor character.

Kaas Society
To outsiders, kaas society usually appears highly chaotic and completely unstructured. Children younger than 10 years live their mothers or are raised by another woman of their mothers home if the former is not possible, but any kaas older than that can pretty much live where they want to. The reality is however much more complicated and sophisticated. Inside a village or town, individuals tend to form groups of people of like mind based on mutual affection and a kind of kinship in spirit. Most young kaas live with their parents until their mid or late teens, at which point they start to get to know the other groups of the community better. As it is a very central part of kaas society, turning away such youths is regarded as highly inappropriate and very poor manners, but it usually becomes clear very soon when their personalties don't match. Having young members joining a group is a great source of pride for kaas and most are eager to welcome such youths as their guests. However, the harmony of the group is extremely important and new members will only be invited to live with the group if there is strong genuine friendship between them. Sometimes childhood friends start their own new groups once they become adults though these are usually lacking any place to live and have barely any income and depend largely on support from older friends and relatives or neighbors for the first few years before they can support themselves. While many of these new groups don't last and their members join larger established groups, those who do manage to get through the years of great poverty intact often endure for the whole life and gain a high reputation.
In rare cases young kaas really are at home with the group they were born into and there is no rule against returning to ones former home. However, they are expected to live for some time with at least three or four other groups to gain other views and perspectives and to learn about the other groups of the community.
There is no form of marriage or inheritance in kaas society. All kaas have to be supported by the group they were born into until they are 10 years old and after that the group has the duty to supply them with everything they will need in their new home, like clothing, a blanket, a knife, and a few bowls and spoons. In most cases, they are allowed to stay until they leave on their own and those groups who can afford it will give more than the bare neccessities to their leaving children. Huts, houses, and in some places caves, are owned communally by the group. As groups split and merge every so often, there are often some abandoned and empty homes to be taken over by anyone who makes claim of them or made an agreement with the former onwners before they left. With large homes in good conditions, the right to first claim is often sold for considerable sums, but since no group can lay claim to more tha one home at a time, this usually results in numerous homes and great amounts of coin changing hands over the span of a few days. In the end, there is always one home for which nobody will pay or is willing to move out of the old one, but these are usually the smallest and poorest ones.
Kaas are extremely protective of their homes. Internal affairs of each group are completly left to be solved by themselves. The identity of a childs father is never asked and that of the woman who claims to be the mother never disputed. However, relationships between people of different groups are regarded as highly shameful. While they have no real concept of love that is different than deep friendship that binds together the members of a group, it implies conflicting priorities and an inability to control ones desires.
In communal disputes, every group speaks with a single voice and it is left to them sort out who speaks on their behalf. Gossiping about the private lives of neighbors is one of the greatest and most dispised vices in kaas society, even if it is about things that are plain for everyone to see. On the downside, kaas are very reluctant to interfere with injustice if it doesn't happen in public places. Since harmony between members is at the center of every group, kaas usually do not invite guests into their home for more than a day or two. But when neighbors offer particularly badly treated individuals to live with them, there is nothing the other group can do about it, since the person is no longer their business. If it can be pulled off without making any implications about what's going on at the other groups home, such actions are highly admired by the rest of the village, as it means having taking care of an outsider until a new home can be found, which is regarded as a significant sacrifice.