Manga Reccomendations

So, I was searching for any manga or webtoon that has something like this:

The MC has low-self esteem, has always been the second choice, over her friend or their siblings. Or the MC is is a rebound or replacement over a past lover, bonus if the MC's love interest still hasn't get over from that said past lover, doesn't matter if it's straigh GL or BL

And an omegaverse where the MC and the ML were not soulmates but but love each other, then the MC/ML's mate came...something like that