A complete N00bz first try at world-building...

[Wyntonian]

Just the second sons? Or second, third, forth, etc?

Yup, it's the rules. In one of the previous posts, that the first son inherits the land and title, second becomes a priest, third becomes a soldier, fourth does other stuff, etc.

Why not instead have him a) be both genders and b) not restrain himself to seducing women? Interesting tidbit of gender equality there.

I think that's a rather excellent idea.