(Y) Yes. Brothers and sisters share the same their parents.
According to the Civil Code Article900 . In paragraph 4,
iv) if there are two or more children, lineal ascendants, or siblings, the share in theinheritance of each shall be divided equally; provided that the share in inheritance of an child out of wedlock shall be one half of the share in inheritance of a child in wedlock, and the share in inheritance of a sibling who shares only one parent with the decedent shall be one half of the share in inheritance of a sibling who shares both parents.
In this case, it means that brothers and sisters who share the same parents (sometimes siblings of whole blood), so the inheritance becomes even.
In addition, if brothers and sisters are dead, their children will be inherited