According to the RCC is it allowed to have more then one wife?
You have several Men living with more the one wife in the bible and you also have the "Let deacons each be the husband of one wife" verse from Timothy. So there are roles that one should consider only having one wife.
If he takes another wife to himself, he shall not diminish her food, her clothing, or her marital rights.
1 Timothy 3:12:
Let deacons each be the husband of one wife, managing their children and their own households well.
And seven women shall take hold of one man in that day, saying, "We will eat our own bread and wear our own clothes, only let us be called by your name; take away our reproach."