Brock had a tough adolescence, though it's mostly just hinted at in the anime (not sure if it's mentioned at all in the manga).

His history on Bulbapedia because I'm too tired to paraphrase: http://bulbapedia.bulbagarden.net/wiki/Brock_(anime)#History

I'd love to see a fic exploring those years when he was trying to raise his siblings on his own while taking command of the Pewter Gym. Also, we know he much prefers caring for pokémon rather than battling, so maybe we can see him solidify that desire as he fights to maintain his family and their gym. Maybe we could see him capture Geodude?