i am a married man with a daughter and felled in love with my sister in law and wish to marry her what do i do

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

In Islam it is forbidden to marry two sisters at the same time as Allaah Says when mentioning the women whom we are forbidden to marry (what means): {…and that you take [in marriage] two sisters simultaneously…}[Quran 4:23] For more benefit, please refer to Fataawa 86633 and 90104.

Therefore, there is no way for you to marry this woman as long as her sister is your wife. Nevertheless, if your wife dies or you divorce her and then her waiting period finishes, then it is permissible for you to marry her sister.

However, it is more appropriate to be patient and not divorce your wife in order to marry her sister, especially if your wife is a pious woman. Divorcing her may lead to many disadvantages, and you are obliged to fear Allaah and avoid thinking about your sister in-law lest you get tempted by her.