Board Thread:General Discussion/@comment-11016223-20130904052318/@comment-6028837-20131118033513

Batboyexe wrote: Karai is Splinters biological daughter, who was kidnapped and raised by Shredder (spoiler alert for anyone that didn't see that one coming) the turtles are Splinters adoptive sons. hence they are somewhat related (not by blood)

in order for that to work she has to have some form of relationship with splinter, she just hates him right now and thats barely a relationship at all. splinter raised the turtles as his sons and have grown a emotional relationship. but he has none with karai so all she is is his biological daughter but not the turtles sister because no relationship other than hate.