Older with younger (18+)

I don’t get what people see in these concentration camp survivors who are emaciated and so skinny their bones are showing through. He has no muscle at all and really isn’t attractive in the least…

I love the older/younger grouping. I find it really hot. But the older guy needs to be fit and not have a beer gut and the younger guy needs to be fit and attractive. Then I like the dynamic to continue by the young man being submissive to the daddy. Mmm, so hot!
The question of what guys like and not like is already discussed with @Brant Stevens.

I find it disgusting to use the word "concentration camp survivor" for a compare in this and generally any other case. There is better wording to express "skinny" or "aneroxic" type of guys than that.