OK, I'll give it a try. Not totally satisfied with my solution, feels like using a lexical crowbar here, but still too close not to mention it. And if my feeling is right that the first one is already the hardest, and the last one is rubbish, then I might be up to something.
Sorry, couldn't resist :-)
So I guess the first brother is
"Hardest" - If you had a kilo(gram?) of the hardest stone (say diamond), that could make you rather rich.
The description of the second sounds quite like my old nemesis
"Hatreds"
to me. Although I don't like too much that this brother comes in plural now.
The third brother would be the
Fedora sporting "RedHats"
The fourth brother seems to be
"Threads"
The fifth gives me the most problems. Maybe the one I have in mind is merely an ugly cousin of this family. I'm thinking of
"Dearths" - With assuming the evil destroyer is Hunger, a horseman of the Apocalypse, who certainly leaves dearths wherever he rides.
If that's mostly correct so far, than this is a family of
anagrams, as the tags heavily suggest
and the last brother is just wasted
or "Trashed", to be precise
Or maybe he is good at bar sports and
He darts?
Or the patron saint of gossip
St Heard
OK, now it's getting silly.
What do you say Jamal? Did I round up the bunch of guys you were looking for?