Ash and Red have no relation what so ever.

I just started rewatching the anime and I noticed some things that debunk the Ash is Red's younger brother theory, so some alternate theories I made are that Ash is Red's older brother, Red and Ash aren't related or the game/manga universe is completely separate from the anime universe. First when Ash first arrives at Oak's Lab Gary says he will make the town of Pallet known to the world, but Red is known as the Champion from Pallet, so why would Gary say he would make Pallet Town known if it is already known because Red came from there. Second is the mere fact that Jessie and James are active. If Red came before Ash, then Team Rocket has already been disbanded but in the anime Team Rocket is still operational, so Red can not have already have started his journey because he disbanded Team Rocket but they still exist in the anime.

EDIT: It is IMPOSSIBLE for Red and Ash to be related. Misty refers to Ash as an only child in S1E52 Princess vs Princess.

EDIT 2: The game/manga universe and the anime universe are completely seperate. In the games Cinibar Island has Blaine's Gym and in the anime it is a resort (S1E57 Riddle Me This)