Is it permissible for a mother to give money to one of her children, and then three years later give the rest of her children an equivalent amount in a property she owns, knowing that all the children were in the same circumstances of need?

What the mother decided regarding giving you the equivalent of the amount she gave your brother achieves the required fairness, and it is precisely the correct thing to do. Equalizing gifts among children oscillates between being obligatory and being recommended. Scholars have differed on the obligation of equalization: The Hanafis, Malikis, and Shafi'is held it to be recommended, while the Hanbalis, Abu Yusuf, Ibn al-Mubarak, Tawus, and Malik in one narration held it to be obligatory, and that one who favors some children over others is sinful and must equalize by either returning the excess given to some or completing the share of the others.