All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.
First of all, your question is ambiguous; as you mentioned that your parents had died, but you did not mention who died before the other, and this has an effect on the answer.
We will base our answer on the grounds that all the inheritance that you asked about belonged to the father and that he did not leave any other heirs than those mentioned in the question when he passed away; so those are four sons (and not three as you mentioned at the beginning), and four daughters. If this is the case, then the inheritance should be divided into 12 shares, each son gets 2 shares, and each daughter gets 1 share.
What the son who divided the inheritance according to his own desire did is a grave mistake because the matter should have been taken to an Islamic court to investigate the estate and divide it with justice.
In the Fataawa Noorun ‘ala Ad-Darb, Shaykh Ibn Baz was asked, “How should the inheritance of the deceased be divided?”
He answered:
“The inheritance should be divided according to the Book of Allaah and the Sunnah of His Messenger . The Quran and Sunnah comprehensively illustrated the rulings on inheritance. The inheritance should be divided by the scholars. The person concerned should submit the question to the scholars or to an Islamic court, and they then divide the inheritance for him. Inheritance differs, it is not the same in all cases.
So if a person’s relative dies, then he should mention the heirs to the court or to a well-known scholar, and he will divide the inheritance between them. For example, he says that a woman died and left her husband and her son; the scholar says, 'The inheritance should be divided between them as follows: the husband gets one fourth, and the rest is for the son, because Allaah says: {And for you is half of what your wives leave if they have no child. But if they have a child, for you is one fourth.} [Quran 4:12] meaning for the husband.'”
Regarding the four residential land lots of which the son claimed that they were bought with his own money, while other heirs claim that he has no right to own them, then this is an issue of dispute, and this requires evidence, and the matter cannot be solved except by referring the case to an Islamic court to study the details, because inheritance is a very complex issue, and it should not be divided without resorting to an Islamic court, if any, in order to fulfill the interests of both the dead and the living.
Allaah knows best.