Is it permissible to disobey one's mother and siblings in private matters, such as sponsoring a child of unknown parentage? And which is more preponderant: the benefit of reward and companionship, or the harm of discord and estrangement? And is this harm considered a valid impediment in Islamic law in this case?

Sponsoring a foundling is one of the best righteous deeds and most rewarding. It falls under the reward of sponsoring an orphan, for a foundling is in the same حكم as an orphan and is in greater need of care and attention.

The Permanent Committee for Issuing Fatwas was asked about children of unknown parentage, and they answered that they are in the حكم of orphans, and whoever sponsors one of them enters into the reward of sponsoring an orphan, due to the generality of the Prophet's (peace and blessings be upon him) saying: "I and the sponsor of an orphan will be in Paradise like this," and he gestured with his forefinger and middle finger, separating them slightly.

The sponsor must not attribute the child to himself or add him to the family card, as this leads to the loss of lineages and rights. The child must be informed that he is a stranger after reaching puberty, unless there is prohibitive suckling.

It is not obligatory to obey the siblings or the mother in abandoning this sponsorship, because obedience is only obligatory in matters that benefit the mother and do not harm the son. Nor is it obligatory to obey the father or mother in divorcing one's wife.

It is also necessary to strive to understand the reasons for the siblings' objection and to remove their misconceptions. If they persist in their stance, there is no harm in sponsoring the foundling and maintaining ties with the siblings as much as you can. The sin is upon them if they sever ties.

If you are infertile and long for a child, this is a legitimate interest. The siblings' request to divorce your wife, while they know that the fault is yours, shows their lack of wisdom. Do not abandon your need and interest for their sake.