Hes 31 even.

Has the same virus's in him as Lisa Trevor plus the progenitor virus.

Kidnapped by Annette Berkin to test viruses and chemicals on when he was 14

When he was 20 he broke out with help from a William Birkin.

When Birkin and Wesker made it to raccoon city Wesker was quite tired and in pain from the virus's constantly trying to take over him. Birkin took him into his lab to help was about to give a injection of antibody producing nanobots Wesker quickly (and tiredly) fled from Birkin. Birkin goes to read Weskers profile and learns that he may have some PTSD from being a unwilling Guinea pig for virus testing. So Birkin designs a patch that can help Wesker. Later Wesker was forcibly brought back in by Ada Wong and as Wesker was quivering like a leaf Birkin shows him the antibody producing patch good for a whole year. so Wesker starts to work for S.T.A.R.S along with a few others like Alexia Ashford William Birkin a girl named Eveline and Ada Wong.

basically Wesker still has the progenitor virus. Birkin pretty much has Sherry's powers.

Here Wesker had a normal childhood and was taught to help people. Berkin's wife is the big bad. She got Wesker when he was a kid and he was in the role of Lisa Trevor. But Wesker kept his intelligence.

Wesker has help from Berkin to keep the cocktail of viruses in his system controlled by a replaceable patch of antiviral medicines that works for a year.

Wesker had a normal childhood before and was the same age as Lisa when he was taken. Alex is there. Wesker is like Chris Redfield so his sister Alex took the role of Claire Redfield.

Also AU Wesker is justifiably terrified of shots or anything that has to be injected. To a point where when it's vaccination season the rest of the S.T.A.R.S (mostly Birkin) have to both calm his justified anxiety from getting a shot and the rest of the group hold Wesker down since he does need to be vaccinated to keep working with them. As you can guess the phobia of injections was given by Annette from the massive amounts of pain the experiments caused him.

His red eyes are from the experiments. hes a little humiliated about it. used to have blue eyes and his hair & skin was frozen in time from the chemicals injected into him namely a cocktail of a sort of Botox-like chemical and some very untested and a dangerous freezing dies Chemical that killed most of the animals that it was tested on. but since the chemicals also reversed his metabolism. He gets cold not warm. still feels cold all the time so usally wears a lot of black for its heat absorbing properties.