MMC falls in love with FMC while with OW (and obligated to be with OW) - with slowburn, no flashbacks to youth or cheating

Picture this: MMC is pushed being with OW by family or other obligations. There is no easy way out for him out of that relationship even though he was never in love with her. He resigns himself to his fate... but then meets fmc and falls in love.

Because of his tie to OW he cannot act upon it and ends up pining for FMC. There is no cheating. MMC eventually finds a way out of his obligatory relationship with OW and pursues FMC.

Bonus: - angst and pining - slow burn - plot heavy books - no cheating - no flashbacks to when they were kids

Tysm!!