Piotr and Illyana Rasputin - better known as Colossus
their dynamic. And I love that at one point in the early comics, 6 year old Illyana gets kidnapped, the X-men rescue her...then they just apparently never bring her back home to Russia. She just kicks around for several issues, this little girl chilling with the X-men. I like to imagine Colossus and the other X-men putting her to bed, having tea parties, needing emergency baby sitters when evil and villainy strike...