Is it Halal for a man to marry a second wife without the wife's family knowing it? Is it Halal for a man to bring the second wife at the first wife's house while the first one is sick in hospital, even though he told her he would never do it?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

There is no restriction on the husband regarding marrying a second wife without the knowledge of the first wife or her parents. The validity of the second marriage and the continuation of the first marriage are not contradictory as the permission to marry more than one wife is given by Allah.

As for taking the second wife to the house where the first wife lives, it is lawful even though it is preferable to avoid it; above all, if the husband has vowed not to do it. In fact, putting two wives in the same house can cause jealousy and hatred between them and it is also a breaking of the promise which should have been fulfilled.

Allah knows best.