Does the father have to treat his children equitably in terms of gift giving, even if his daughters are married?
Question

My father died thirteen years ago, leaving behind some debt and some properties. My two brothers paid off my father’s debt and paid the costs of my marriage and my education. During his lifetime, my father purchased two pieces of property and registered them in the names of some of my brothers. He also stated clearly on more than one occasion that he would buy a property for me and register it in my name too. Please note that all my sisters were married at that time, and now they are saying that my brothers do not have any right to keep these properties, because Islam forbids favouring some children over others. Does the hadith which speak of that apply to married daughters too?
Praise be to Allah.Firstly:
It is obligatory to treat both sons and daughters equitably in terms of inheritance and gift giving.
Being equitable is obligatory with regard to inheritance, so the estate must be divided equitably, as Allah, may He be exalted, divided it in His book: with each male having a share equal to the share of two females, whether the females are married or unmarried. So it is not permissible to deprive the female of her share because of marriage.
Allah, may He be exalted, says (interpretation of the meaning):
{Allah instructs you concerning your children: for the male, what is equal to the share of two females. But if there are [only] daughters, two or more, for them is two thirds of one's estate. And if there is only one, for her is half. And for one's parents, to each one of them is a sixth of his estate if he left children. But if he had no children and the parents [alone] inherit from him, then for his mother is one third. And if he had brothers [or sisters], for his mother is a sixth, after any bequest he [may have] made or debt. Your parents or your children - you know not which of them are nearest to you in benefit. [These shares are] an obligation [imposed] by Allah . Indeed, Allah is ever Knowing and Wise} [an-Nisa’ 4:11].
Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allah have mercy on him) was asked:
We have some customs and traditions which deprive women of inheritance after they get married. Please note that the women themselves do not ask for their rights. What is the Islamic ruling, in your view, O Shaykh?
He (may Allah have mercy on him) replied: Marriage does not deprive anyone of inheritance, and these traditions are invalid. The fact that she got married, and that she is the sister of the deceased, or the daughter of the deceased, or the wife of the deceased, does not mean that she should be deprived of her right. If someone dies and leaves behind five daughters, or ten daughters, some of whom are married and some of whom are not married, they all have a share in the estate. Or if someone dies and leaves behind sisters, or he dies and leaves behind his mother and she is married, each person should be given his or her share. Marriage is not a reason to deprive anyone of his or her share, and taking this matter lightly is a reprehensible action. But if the woman is of sound mind and gives up her share to the one who is not married, and she says: I am in no need because I am married, praise be to Allah, and I give you my share – if she gives it up, and she is of sound mind and mature thinking, and she says to her sisters: I give my share to you, there is nothing wrong with that. But if she is deprived of her share because she is married, that is not permissible."(Fataawa Noor ‘ala ad-Darb 19/443).