You can also 'buy' a wife.
If your current wife is gravid and 'not available' to perform her wifely duties (not cleaning the house, mind you) then the husband can temporarily marry another wife who will 'perform' those duties.
It could last six months, a year...eternity I guess. It's a contract agreed to by both sides.
Usually the new wife (and there is a slightly derogatory term if I remember correctly) is poor, ala single mother, but attractive for obvious reasons.
I guess only the poor men go around buggering little boys for their jollies.