Is it permissible for the father to sell his property to one of his sons and not the other?
Question

                My father 81 y old financially comfortable, has sold 2 properties to my brother in a very very low price, claiming that he needs the money! I feel there is unjustice here! do I have the right from islamic point to be upset? knowing that my brother claims if I donnt accept his fantastic offer,it would go to someone else stranger to the family?.
Praise be to Allah.Firstly: 
If the 
    father intended, by selling this property to one of his sons and not the 
    others for a very cheap price, to show preference towards this son over his 
    brothers and to single him out to acquire some of his property by means of a 
    superficial commercial transaction, this is a haraam trick to commit sin and 
    transgression. It is not permissible for the Muslim who is about to meet 
    Allah -- as he has reached the age of 80 -- to do this, thus causing 
    resentment and grudges among his sons and going against the command of the 
    Prophet (blessings and peace of Allah be upon him) who said: “… Fear Allaah 
    and treat your children fairly.” Narrated by al-Bukhaari (2398) and Muslim 
    (3055). 
But if your 
    father did not intend to do such a trick; rather he actually wanted to sell 
    his property to any purchaser as your brother claims, because he was in 
    urgent need of the money, then he should sell it for the market price, and 
    there is nothing wrong with his reducing the price a little for his son, as 
    people customarily do such things when involved n similar transactions.  
If more than 
    one of a man’s children wanted to buy his property and all of them wanted to 
    buy it for a similar price, then he should cast lots among them, and the one 
    whose name is drawn will have the right to buy the house, so as to avoid any 
    hint of favouritism towards one of his sons with regard to giving and so 
    that all his sons will be free from resentment, grudges, shunning and envy 
    towards one another. 
Secondly: 
If the 
    father did do wrong and favoured one of his sons, and the others did not 
    approve of that, then it is their right to object to that sale and to ask 
    him to cancel it. They could offer to help him financially, if he needs it, 
    in the form of a loan, if he really was in need of money; or they could ask 
    him to treat them fairly with regard to giving, either by giving all of them 
    property like he gave to that son, or by sharing out among them from his 
    wealth and giving an amount equal to the difference between the price for 
    which his son bought the house and the price for which similar properties 
    are usually bought.  
Thirdly: 
We would 
    remind all of you brothers that the ties of kinship that exist among you are 
    greater than this insignificant worldly matter and such matters should not 
    lead you to hate one another. With regard to what has happened among you of 
    differences, strive to remove the causes of that in the best manner, and 
    give precedence over everything else to the ties of kinship that existed 
    between you. 
Shaykh 
    Saalih al-Fawzaan (may Allah preserve him) was asked the following question:
I am a man 
    whom Allah has decreed should suffer some disease in his right leg and the 
    doctors have decided to amputate it, which means that I will not be able to 
    work, and I am the head of a large family. I have three brothers, but my 
    father has sold his farmland to my three brothers. Because I am unable to 
    buy any part of it, I did not get anything. It is what my father did valid 
    or do I have the right to ask for my share without buying or selling? 
He replied: 
If he sold 
    this farmland to your brothers in a valid transaction in which there was no 
    trickery or compulsion -- rather he sold it to them as he would sell it to 
    anyone else for the full price, and he did not let them off any part of the 
    price; rather he received the price in full from them -- then there is 
    nothing wrong with that and you do not have the right to object, because 
    there is no favouritism involved in that and he was not singling them out 
    for any money and excluding you. 
But if that 
    was not the case, and it was a sale that involved trickery and he was 
    lenient towards them concerning that and showed favouritism towards them, 
    then that is not permissible, because it is unfair and the father must treat 
    his children equally with regard to giving gifts, and it is not permissible 
    for him to single some of them out to the exclusion of others, because the 
    Prophet (blessings and peace of Allah be upon him) said: “… Fear Allaah and 
    treat your children fairly.” The father is obliged to treat the children 
    fairly with regard to giving gifts to them, and it is not permissible for 
    him to favour some of them over others. End quote. 
Majmoo’ 
    Fataawa al-Shaykh Saalih al-Fawzaan, 2/594, 595 
And Allah knows best.
    See also the answer to question number
    114659 and
    119655.