If Brock isn't at the gym in Pokémon, you can try checking the surrounding areas like Route 3 or the Pokémon Center, as he may be there. You can also engage with other trainers or NPCs to gather hints about his whereabouts. If you're still unable to find him, consider progressing through the game to see if he returns later or if you need to complete other tasks first.
No,but you can battle them because they are gym leaders. In the classic pokemon show, Ash,Misty,and Brock had a journey together.
In the Pewter City gym, then once you get his phone number you can re-battle him in the Fighting Dojo in Saffron
Pewter Gym.
Brock's Gym is located in pewter city. He owns rock type Pokemon so use a water or fight type Pokemon in your battle.
I know Brock, and probally Misty. Possibly Giovanni
Brock's gym is in Pewter City.
Pewter City
By his family
brock is the 6th gymleader
the first gym leader is brock.
You go to Pewter City and challenge Brock.
brock