How can children know if there has been an equitable distribution of gifts among them, and should they do something about it, especially if the gifts were given at different times and under different circumstances?

The issue of the obligation to return an unfair gift after the father's death is subject to differing opinions. The majority of scholars hold that such a gift becomes final after his death if it was taken possession of during his lifetime. The recipient is not obligated to return it to the estate, though it is commendable for him to do so. As for how to ascertain a father's unfairness in gifting, this is generally known if the father singled out one of his children for a gift to the exclusion of the others. However, a gift is not considered unfair if he gave to one child at one time and to another at a different time, or if he singled out some of them due to a need or a legitimate Sharia-compliant reason, such as illness, a large family, or preoccupation with seeking knowledge, or if he withheld from some due to their transgression. As for spending on children, equality is not obligatory; rather, it should be according to their different needs.