What is the ruling on burying a son above his deceased father when the father was angry with him due to his disobedience?

It is not permissible to bury two or more persons in one grave except out of necessity. It is also not permissible to exhume a grave once the earth has been piled over it, as scholars consider this to be a forbidden mutilation. Generally, a grave is in one of two states: First, it is dilapidated and what is within it has decayed, in which case it is permissible to bury in it. Second, there remains a trace of the deceased within it, in which case it is not permissible to exhume it or violate the sanctity of the Muslim dead within it. The issue of a father's anger towards his son who was buried with him has no bearing on the ruling.