Think he then had to support both “wives”. But women could also divorce men in that scenario afaik, and it was a kind of fault divorce system so would have been punitive on the man in cases of adultery I imagine. However, while there was a kind of standard brehon law at any given time (it wasn’t a static system) its practice would vary between clans, and we don’t know as much as we would like about even the standard versions truth be told.