Marvin Branagh is a minor character who plays minor roles in Resident Evil 2 and Resident Evil 3: Nemesis
Resident Evil 2
Marvin is encountered early on in the game in both Leon S. Kennedy and Claire Redfield's A scenario in an R.P.D. office. He is found fatally wounded but manages to give the two a key to open the doors in the R.P.D. main hall. He is later encountered as a zombie. The player can choose to either kill him or avoid him completely. Like most zombified turned characters, Marvin is harder to kill than most regular zombies. A head shot with a shot gun will do some good though.
Resident Evil 3
Since Resident Evil 3 plays as a prequel, Marvin is only encountered unconscious in the same office Leon and claire will find him in.