Islam permits a man to marry up to four wives. This custom still occurs and (as a generalisation) many families will have at least one man who has two or more wives.
This practice is endorsed by the Koran (4:2 & 4:3) which says,
“Give orphans the property which belongs to them. Do not exchange their valuables of worthless things or cheat them of their possessions; for this would surely be a great sin. If you fear that you cannot treat orphan (girls) with fairness, then you may marry other women who seem good to you; two, three or four of them. But if you fear that you cannot maintain equality among them, marry one only or any slave-girls you may own. This will make it easier for you to avoid injustice.”
I remember watching one man who had two wives being shuttled between the two houses and feeling sorry for him; I couldn't imagine what it must be like to have no where he could call his own home. That was my European perspective on his situation, he seemed genuinely happy with the situation ...
The following poetry quote is about the difficulty of taking more than one wife and comes from, ‘The Perfumed Garden’. This is an Arabic erotic book which is thought to have been written in the 1500’s and translated into English by the explorer Richard Burton in the late 1800’s.
“By reason of my ignorance I have married two wives - and why do you complain, O husband of two wives? I said to myself, I shall be like a lamb between them; I shall take my pleasure upon the bosoms of my two sheep, and I have become like a ram between two female jackals, days follow upon days, and nights upon nights, and their yoke bears me down during both days and nights. If I am kind to one, the other gets vexed. And so I cannot escape from these two furies. If you want to live well and with a free heart, and with your hands unclenched, then do not marry. If you must wed, then marry one wife only: One alone is enough to satisfy two armies.”
Two Saudi women married to the same man and living in the same house, lived next door to another couple and had become friends with the wife. When next door neighbour died the woman begged their husband to marry the neighbour’s widow. After some discussion and thought their husband agreed and so did the widow next door and now all three live together in one house.