I've never heard of a disabled person losing their OWN SSI or SS benefits due to a termination of parental rights. Remember, very few parents who have their rights terminated are actually criminally charged. The penalty is loss of the child. IME, abuse must be physically very severe or involving sex abuse for there to be criminal charges brought. The charges typically stay at the Family Court level.
Concerning gun ownership, I'm not a gun owner so I don't really know the rights involved but I cannot imagine that SSI or SS benefits could be discontinued due to gun ownership. I do believe that we'd have more than a few people "up in arms" about that!!
I'm not positive but I don't think that a convicted criminal loses their benefits either, unless they are incarcerated. I'll have to check. In any case, if the children were receiving benefits based on disability or survivor's benefits those would follow them into foster care or adoption and become a "patch" in their funding resources.
Concerning this infant, was there information I missed concerning a disability for her?