Gamefreak can't get their world building/multiverse right, so there are multiple unnecessary incarnations of the same characters throughout the series. For example, there are 5 Reds.

>Classic Red (Original from the timeline where Megas don't exist, ORAS confirms the existence of this timeline)
>Modern Red (FRLG counterpart, from the current active timeline)
>Adult Modern Red (post-timeskip FRLG counterpart who makes appearances in SM which would mean SM takes place years after BW2, as Red competes in the PWT, still with his FRLG design)
>Classic Modern Red (appears in the 3rd confirmed existing timeline introduced in LGPE, taking place around the same time period as original Kanto saga, Red, Blue, and Green are usurped by even stronger and younger trainers from Pallet Town, Chase and Elaine. Mega Evolutions exist in this timeline, despite many of the character and location designs in LGPE styled after RBY and not FRLG, most notably is Red and Blue donning their original clothes from the original games.
>Fusion Red (introduced in Masters. This Red wears clothing called a Sygna Suit, resembling an updated and edgier take on his classic clothing. His hair seems to be a much darker shade of brown than his FRLG counterpart. Nothing will ever be confirmed though, and who gives a shit at this point)
>and then there's the Red from the manga which is a more cheerful guy and has better hair, but GF has nothing to do with that, and probably didn't have anything to do with the designs in Masters.

Also, Satoshi/Ash is basically a disfigured Red from a bizzarro universe.