Head Canon, Coldflash + Vampire?
Okay, so I’ve got a THING about Barry as a vampire, so I’m gonna do this from that mind set, hope that’s cool Nonnie.
Barry was changed young, during the Roman Empire. He was the son of a senator and lived a sheltered life but when Spartacus went through freeing people, a vamp caught Barry and he got turned.
Now, don’t believe this hype about vampires can’t go out in the sun, cause if he keeps himself feed well, it only looks like a small sunburn after a few hours, and that usually clears up really quick for Barry.
Barry spends centuries traveling around, learning to feed without killing and learning how to control his speed and strength so he passes off as a normal human.
Barry actually meets Len twice when the latter is a teen but he never really registers until Barry meets the man again when he’s 23 and trying to rob Barry’s home. Barry’s first instinct is to act like a normal human but God
he’s never smelt someone, anyone like Len before, so he outs himself for the first time in 300 hundred years.It takes a while but Barry earns Len’s trust and by default Mick and Lisa’s as well. It helps that as soon as Barry learns what Lewis is like and the fact Lisa is still stuck under the man’s roof, he not going to let that stand and Lewis wouldn’t be the first life Barry’s taken (he may have gone a little crazy during the WW1 when his then fiance, Iris, was killed during a raid on London where she worked). So killing Lewis is no skin off Barry’s nose.
It’s still pretty rocky but Len and Barry eventually work things out, and have a long lasting relationship. Barry respects the fact Len chooses not to change until he’s almost 45, because that’s when Mick and Lisa accidentally get changed by an old foe of Barry’s.
(But that’s a story for another time.)