Yes, a person who is not mentally challenged can divorce a person who is mentally challenged would have to be proven they are mentally challenged), but they would have to let the courts decide in the provisions of the divorce what you would pay to help sustain the lifestyle of the mentally challenged person.
"Mentally challenged" is a euphemism for mentally retarded, or having a low IQ or mental disabilities this means that someone who would be mentally challenged wouldn't do as well as their classmates. when your not physically disabled (wheelchair)
Most states would consider that to be mentally challenged.
Second cousin.
Your half second cousin's son would be your second cousin once removed.
Your child would be the second cousin to your cousin.
Yes. Your second cousin would be your cousin's son or daughter. This is different from a niece or nephew because a nephew would be your sister's/brother's son.
Your second cousin, twice removed, is the grandchild of your second cousin (the great great grandchild of your great aunt or great uncle) or the second cousin of your grandparent.
In the u.k the word "retarded" would be seen as quite offensive. We use terms such as "mental impairment/having a learning difficulty/cognitive disability". However, through different research, in response to your question, I have heard the term "mentally challenged" and "mentally retarded".
Your cousin's son is your cousin, once removed. For example, if your cousin is a second cousin, the son is your second cousin, once removed.
Your first cousin's grandson is your first cousin, twice removed. Your second cousin's grandson is your second cousin, twice removed.
Your first cousin's daughter is first cousin once removed to your grandson, and he to her. Your second cousin's daughter is second cousin once removed to your grandson, and he to her.