Complex sentence: If the like-named men are indeed different people, they could well have been closely related, with the former being a son of Dyfnwal, and the latter perhaps a son of Dyfnwal's son, Máel Coluim.
Split into simpler sentences: If the like-named men are indeed different people, they could well have been closely related. Whilst the former may have been a son of Dyfnwal himself, the latter could well have been a son of Dyfnwal's son, Máel Coluim.