mmem's manga / #siblings not related by blood(4)

Maybe it’s bc I skipped around but I kept feeling like the couple were constantly flip flopping! Even in the end, story ends w ML proposing then side story takes place 4ish yrs late & they still aren’t married and MC’s planning to propose but ML’s acting all sad and like he’s planning on breaking up only for MC to interrupt him and they end up engaged??? What is this? And Like why are some of these conflicts even a thing and why can’t he have a kid w a beta, apparently everyone else is lol.