Chimera: When You're Your Own Twin.

Lydia Fairchild was facing an uphill battle in court to prove that she's the mother to her children. Fairchild was about to lose her children; Social Services accused her of welfare fraud and was about to take her children away from her.

No one believed that she was the mother to her children because her DNA didn't match theirs - and DNA, the court said, didn't lie.

But in this case, turned out that it did - Lydia had a rare disorder called chimerism: she was a chimera (she had different DNAs in her tissues) - essentially she was her own twin.

Read more of this weird medical mystery: Link