The only enemies that I know of were the Boleyn's; Anne, George and Mary, during the reign of Henry and Anne (1533 - 1536). I know that Jane had her younger brothers, Thomas and Edward and her family...
That happens to me... I try to steer them away from my enemy, or talk to them about how you feel.But remember if you TELL them not to you'll seem control-freakish, and you don't own her/him. Just...
you should still be friends with her/him just do not gossip about your enemy because then the friend will go and tell and that leads to major drama and drama is something you dont want to get into it...