Who is more entitled to financially support a widow: her son or her brother? And are there conditions that would give preference to one over the other?

A wealthy son must spend on his poor parents because he is part of them, and he is more obligated than anyone else to provide for them. If the mother is a poor widow and her son is wealthy, then he has a greater right to spend on her than her brother. If her son is poor, then, according to some scholars, her wealthy brother is responsible for her maintenance.