Can a father write his will to whomsoever he wishes of his property other than his son/sons stating that it is his own will and property and he would give to anybody he wishes. Is this authority given by Shari’ah?

Everyone has his right on his property but after death, he can write will on his 1/3 estate. For rest 2/3 he can give it to anyone if inheritors agree on his will otherwise no.