A man and his wife, son and daughter died in an accident; how should their estates be divided?

He died and left behind a wife, his parents, a son and daughter

Can he donate his share of the inheritance before it is divided for memorisation of the Qur’aan?

He died and left behind two wives, four sons and two daughters

If a woman dies and leaves behind full siblings or half siblings through the mother

Their parents made bequests before they died stating that the estate was to be divided in a specific manner; do they have to follow that?

If he dies and does not leave behind anyone but a brother or sister through his mother

He agreed with his father that he would pay the Hajj expenses for his mother, then his father died before he could take her

She died and left behind a husband, children, a full brother and a half-sister through her mother

She died and left behind a husband, three sons and six daughters