The quote leaves out one important part of the equation... since the men are residing in their mother's houses along with their siblings, a man becomes the "father" to his sister's children, sharing in childcare and being a family. They are not cut off from the next generation.
He still gets to bring up kids. Just not his own (because who knows which are his own?). In terms of genetics, though, he is guaranteed to share genes with his sister's children.