I guess it could be a possibility, but it's highly unlikely to mean that in this sentence.
Dyn a gwraig could mean "a man and a wife", but not likely his own wife, just some man and some other wife, which sounds weird. So in this case it's best to translate gwraig as "woman": "a man and (a) woman".
If you want to say "a man and wife" i.e. the wife is his wife, then you'd probably say either dyn a'i wraig "a man and his wife" or gŵr a gwraig "a husband and wife". In both these cases you'd translate gwraig as "wife".