MMM ... Funny that you bring that up now! E is 3.5 also and is just now getting curious. She started asking questions last week after we hung out with the family who gave us their extra embryos. The one woman is our egg donor, for lack of a better description. They fertilized her eggs with donor sperm, and the other woman carried their two children. So their children are E and H's full siblings. This sparked loads of questions about eggs and sperm and mamas and papas and adoption and pregnancy and such. I can tell that she's really thinking about it because she'll come up with questions out of the blue. Example: "Mama, did Baba give you her sperm?"
It's neat to see her figuring things out. Our approach is honest and frank. Curious to hear from others!
Thanks to everyone who commented on my beloved friend. I appreciate it.