I feel like this is all I ever post about

So, my sister isn't my sister after all; she's my (drum roll, please) cousin once removed. For that matter, my teenage brother is actually my uncle. This gets back to the extended-family-in-Africa-is-really-extended concept that I seem to have a much worse grasp of than I would have thought only two nights ago.

It all started on Sunday, when a women who lives down the street from me told me to say some word I don't remember to my mama. The word turned out to be "Thank you" in the tribal language which they share. Then, two nights ago, my "brother" told me to say the same word to my "sister". She replied with a phrase in the tribal language. When I asked what it meant my "sister" wouldn't tell me and my "brother" only shrugged. I asked him why he didn't know and he said that he didn't speak that language. Odd. I asked him what languages he did speak, one of which my "sister" didn't know. Curiouser and curiouser. After a long series of questions I ascertained their lineage to the best of my abilities. The baby is still my host brother-in-the-American-sense.

This explains why my parents look so young, spaced their children so wide (two teens and a 4 month old), and have so few children; they are so young, didn't space their children widely, and have only just started their family. Other questions remain, however:

Is the woman that first taught me the other word for "thank you" actually my mama's sister, as they all claim?
Is the man across the street actually their brother, as they all claim?
Are they all just members of the same tribe?
Why does my uncle ("brother"), who says he is my mama's brother, not speak my mama's tribal language?

Every new thing I learn just leads to more questions...