Also if we found a fossilised bonobo chimp we might assume it is our ancestor but bonobo chimps coexist with us.
I have Welsh ancestry. The thieves and other folks of Wales coexist with me.
And no, bonobos are not a ancestor to humans, just like the people now in Wales aren't ancestors to Coragyps. Don't make the mistake, though (I don't know that you are....) of thinking that Species A must be extinct for Species A1, a descendant group of A, to exist. We still have wolves......