Can someone ever be denied his / her share in inheritance?
If an adult offspring has rebelled and left the family home, and no longer practices Islam or has adopted another religion, should such a child be included in the father’s will?
It is not the question of father’s will that is important in this case. You don’t normally will in the case of those relatives who have already been covered in the Quranic law of inheritance. In case a person wills anything other than what has been mentioned in the law of inheritance, it would be considered inapplicable. The father would, in all probability, not will anything for him. The real question is whether the society allows such a child to share in the wealth the father has bequeathed according to the law of inheritance.
The reason why such a question arises is that the Quran mentions that the rationale behind the peculiar shares the Almighty has suggested for various close relatives, is that “you don’t know who amongst them (close relatives) is closer to you in benefit” (Quran; 4:11). Since a child who rebels against the father or the family has terminated all possibilities of benefiting his family, he is likely to not be considered eligible to benefit from the father’s wealth after his death. This decision can be taken by the father himself and can be expressed in a will or can also be taken by a competent court.
The question of change in religion may or may not fall into that category. If despite changing his religion, the child has been dutiful towards his parents’ needs, his right may not be terminated. Otherwise, his case could be similar to the rebellious child’s case. Again, it would be decided by either the father or the court. And Allah knows best.