@Shadow the Hedgehog
Boy oh boy, will this confuse you.
So those characters are all part of alternate realities. Heavy, Soldier, and Scout are from one (technically the current, but kinda not), while First!Medic is from the current, taking place after killing his boss and his boss’ daughter. He then summons Second!Medic, who is from the original timeline that the group of three are part of. He then kills himself because he needs to set the universe right.