Does the uncle own the plot of land that the father intended to give him before his death, knowing that the heirs are two sons and three daughters?

If your father intended to give the land to his brother but died before doing so, and he did not make a legally valid will to that effect, then the land belongs to the heirs. However, if he willed that the land be given to his brother after his death, this is a bequest. Since your father has a son, his brother does not inherit from him due to the son’s exclusionary inheritance, which completely disinherits the brother. Therefore, his bequest to his brother is a bequest to a non-heir, and it is valid only within the limits of one-third of his estate. If the land does not exceed one-third of your father's estate, his brother, the legatee, takes it. If it exceeds one-third, his brother takes only the amount equivalent to one-third, and anything beyond that goes to the heirs.