Family Tree

Current three and the Sisters were at the park yesterday. A mom apparently asked Big Sister if she was the new guy's sister. Her answer (not in its entirety but pretty close):

"No, he's not my brother. He's HER brother and HIS foster brother. And HER foster brother is HIM and HIS foster sister is HER and HIS foster brother is HIM. And that girl in the blue jacket? She's MY sister. But not my foster sister."

The lady then asked a question that I couldn't hear.

"No, we used to be foster kids but now we aren't. She's still our mom but now we're just friends."

Pretty sure the lady gave up after that.