My brother in law is mentally disabled, he gets a $712.00 per month . He's father is deceased now, took care of him all of his life. Is he ( the son) entitled to collect some of his father's SS money? The $712.00 isn't enough for him to find housing to live.
If your brother-in-law is unmarried and he became disabled prior to age 22, then he may be able to qualify for disabled adult child's (DAC) benefits from his father's account. You don't mention what type of disability benefits your brother-in-law currently receives, but if it's from Social Security then he couldn't receive more than one full benefit at the same time. If he qualifies for more than one Social Security benefit, he could basically only receive the highest of the benefit rates for which he's eligible.