Board Thread:General Discussion/@comment-24.150.191.44-20130401024547/@comment-184.88.179.174-20130401153618

That's what everyone is saying though it's not confirmed in the show. The only clue we have is in "The Alien Agenda" when Shredder told Karai,"Remember what Hamato Yoshi has done to us" which tells us that Shredder did kidnap Miwa as a baby and raised her with lies about how Splinter ruined their lives when it was the other way around.