Is it permissible to marry a brother's widow in order to sponsor her children, despite the mother's disapproval and doubts about the widow's religiosity?

Seeking to provide for widows and sponsoring orphans are among the most meritorious acts of devotion and the best of worship. One who strives to help a widow and a needy person is like a mujahid (fighter) in the cause of Allah, and the one who sponsors an orphan will be with the Prophet, may Allah’s prayers and peace be upon him, in Paradise. If the orphan is a relative, such as a nephew, the matter becomes even more emphasized.

It is advisable to perform Istikhara (prayer for guidance) and consult knowledgeable people. If the matter seems appropriate, then convincing your mother is obligatory. If she agrees, then that is good; otherwise, you must abandon the matter, because obeying her is obligatory. It is possible to look after the welfare of your nephews without marrying their mother.

It is necessary to avoid temptation, not to sit alone with the widow, and to avoid private seclusion with her before marriage. It is not permissible to accuse her of sorcery unless there is conclusive proof.