I don’t think we’re on the same page.

she’s too good for him

It doesn’t seem like either of them are breaking their backs to put effort into their relationship. Also, what kind of 22 year old allows their parents to dictate their life to that extent?

doesn’t deserve to have her life fucked over with

Sounds like she has that part taken care of.

The brother seems to actually be developing a real relationship with the coworker. The other girl is just someone who comes around and doesn’t do anything with him. Ideally, the brother should just tell the girl to stop coming over. Why OP gives a shit about any of this is beyond me