That depends....
The wording (from the PFsrd, emphasis mine)
On the other hand you have something like the Brood MasterThis indicates the maximum number of natural attacks that the eidolon is allowed to possess at the given level. If the eidolon is at its maximum, it cannot take evolutions that grant additional natural attacks. This does not include attacks made with weapons.
The problem is that at Broodmaster 2, you can have 2 Eidolons out, but a Max Attack limit of 3. What if you decided one of your Eidolons was a Biped and the other a Serpentine?the rest of the eidolons’ base statistics must be divided between the eidolons, including Hit Dice (minimum 1), skill points, number of feats, armor bonus, Str/Dex bonus, evolution pool (but see below), and maximum number of natural attacks.
Or at Broodmaster 8, when you can have 4 Eidolons, but a Max Attack limit of only 4?
My final answer?
As with most things Summoner, ask your DM.