So I finally talked to my manager.

Splitting myself into 4 persons role is absolutely not possible.

I told him that I want to focus on the project that I'm leading - in which, is being more fair and beneficial for the project team.

He agreed to let me take more time to focus on the project.

My role has reduced from 4 persons role -> 2.5 persons

That could mean two things:

1) My colleague will share my burden.
2) I need to close the project beautifully. Cos now there's no reason why I can't.