This is what I found about second marriage and it says that if family is established, couple have childern than a second mariage would be detrimantle to the family and therefor should not be allowed, end of story. And in my openion is real Islam.
Wife's Permission for Second Marriage
Question
If a couple is married and has three children, the husband and wife like each other and the husband now wants to marry another woman, is it compulsory for the husband to get permission from her wife for second marriage or can he do this without the consent of first wife and marry the second woman in a hidden way. He does not want to divorce the first wife and wants to keep both in his home. Please tell me about the permission of first wife in accordance with Quran and the Sunnah.
Response
Firstly, I must let you know that the entire concept of a Nikah1 is that it is not 'hidden'. A Nikah must be announced in the society the person is living in. Therefore, I believe it would be wrong to take a second wife in marriage without the first wife and/or the children knowing about it. This is in addition to the social circle of both the persons getting married.
Secondly, with respect to the permission of the first wife, there are two different but related issues. First is whether the Shari'ah has imposed any additional requirements specific to a second marriage. Both Quran and the Sunnah are devoid of any additional requirements and, therefore, as far as the Shariah is concerned the second marriage can be undertaken without an explicit permission from the first wife. The second issue would be that of the law of the land where the person is residing. It is possible that the law of that particular region does not allow second marriage or requires the permission of the first wife for second marriage. Such a law would, then, have to be followed even though it may have no jurisdiction in the Shari'ah.
Thirdly, I must add that if second marriage will imbalance the first marriage and the family structure that is already established, then one must not believe that they have a free right of undertaking the second marriage. Islam has not given the permission to take multiple marriages so that the family structure is destroyed. In fact, it has done the same in order to protect the families! Therefore, if a second marriage is undertaken that adversely affects one's first marriage and the children, then Islam does not condone it. This is also evident from the way Quran has allowed permission for marriage for instance. In the context of widows, where widows are the weak party, Quran has allowed a second marriage in order to protect them - the weak. However, with respect to the rights of the wives, Quran has recommended that one may marry only one if they will be unable to fulfill the rights of all of them, once again protecting one's existing wife, which is the weak party in this case.
http://www.omeriqbal.com/a/37