Elves and half-elves have the fey ancestry racial trait; however, I have noticed that the fey creatures do not have the same trait. It seems illogical that fey would not have the benefits of Fey Ancestry.

In my current campaign, I have a Half-elf warlock that has taken a sprite familiar. Would it be unbalancing to give the sprite familiar the traits of fey ancestry (adv against charm and immunity to magical sleep)?