can you unlock new characters if you start the game coop?

[Yogi]

so i have no one unlocked i have to do runs but will they unlock if these runs are with a friend? also can two people play the same hero?

[Birgit]

I just did a coop run with my boyfriend (first ever run, no singleplayer done yet) and obviously we both were the ironclad, but we unlocked silent.

so it seems like yes it will unlock even in coop

[Yogi]

can you unlock everything in multiplayer?

[Big Sneeze]

Yes.
The game will give you a tutorial pop-up advising you to play at least one run in single player, but this is completely unnecessary, you can play co-op from the very first run and make progression unlocks.