Basically and traditionally, it is prohibited or not allowed by each party. Most of people who knows a guy having 2 women thinks he is a playboy. Base on what's happening in real life, I can say that some men and women here in the middle east are just having a relationship for fun, for money, to escape loneliness and to have a sex partner.
But there are some men and women who are being in love...and became a victim of love...a so called " right love at the wrong time" . The worst fact with this kind of relationship is that when the guy is married already. Sometimes a man can find a true love in other woman....a better love...a love that can lead in a long serious relationship, but the question there is that " up to what extent they can move and carry this kind of relationship".

Have a nice day!