Is it permissible for a father or mother to write over some of their property to certain children, to the exclusion of their other siblings, in order to achieve justice and equality among the children?

It is permissible for parents to specify one of their children for a gift if that child is in need due to poverty, illness, having many dependents, or seeking knowledge. The evidence for this is what was reported from Imam Ahmad. However, if the gift is for a reason that is not considered valid, then the parents must be just and equitable among their children. Based on this, if the gift to your two brothers was due to a valid need, then you are not obligated to receive a similar amount. But if there was no justification for it, then they must give you the same as they gave them, otherwise, they must retract what they gave to your two brothers to achieve justice.