Short answer. Only the nearest relatives in degree receive it. Under Article 959, a general disposition in favor of "relatives" means the closest living relatives of the testator, not every person related to him. More distant relatives are excluded once nearer ones are alive and qualified.
What the law says
A disposition made in general terms in favor of the testator's relatives shall be understood to be in favor of those nearest in degree.
Civil Code, Article 959 — A Disposition in Favour of 'Relatives'. Read the full provision →
Why vague words like "relatives" need a legal rule
Testators sometimes use casual, all-encompassing words without thinking about how far the circle extends. "Relatives" in ordinary conversation could mean immediate family, or it could mean every cousin to the fourth degree. The law could not leave that question open — it would produce endless disputes over who qualifies. Article 959 settles it with a clear rule of proximity: the word refers only to those who stand nearest in degree to the testator.
How degree of relationship works
In succession law, "degree" is counted by the number of steps connecting two persons through common ancestors. Children are one degree from a parent. Siblings are two degrees from each other (up one step to the parent, down one step to the sibling). Nephews and nieces are three degrees from an uncle or aunt. The rule in Article 959 means that if the testator left children, the children take — grandchildren and more distant descendants are excluded because the children are nearer. If there are no children, grandchildren would be the nearest, and so on.
Who shares when several relatives are equally near
When two or more relatives stand at the same degree — for example, three surviving children — they share the disposition equally among themselves. None of them has priority over the others by reason of age or sex. The general rule of equal sharing among relatives of equal degree applies unless the will provides otherwise, which in this case it does not because the bequest was in general terms.
What this means for your family situation
Work out who is alive and what degree they stand in relation to your father. The nearest surviving relatives in the closest degree take everything under this disposition. If your father had living children, the property goes to them and not to siblings, nieces, nephews, or more distant kin. If there are no children, it passes to the next nearest class. The estate proceedings will confirm who qualifies, and if there is a dispute about degree or about who was living at the time of the testator's death, that is decided by the court handling the settlement.