Board Thread:Fun and Games/@comment-25495053-20141003162209/@comment-26353309-20150420210949

If you go to Venus' wiki page, you'll see that she's not just a friend, she's their secret sister. Hope that helps. (Spoiler) In the Invasion, Part 2, you can catch a glimpse of a picture of a girl with in cursive the name "Venus" which resembles their sister.