Uh I'm really confused rn, soooooo did he date bothe pf them?

Yes

Does the brothers know that red or maroon or brown hair guy (srry i forgot the name ._. ) is dating both of them?

Also yes!! Maru remarked before things blew up that nothing had to change once they were dating (so brother can continue the relationship).

In the car before kissing MC also joked about whether they're actually dating (him and Maru) because Maru told the brother about him coming back but not him.

._.