Question

SPOILER




Though I don't remember all the details
No, they don't end up together. They changed the details in the webtoon from the novel. Webtoon - Diana got dethroned and the two divorced.

Novel - diana doesn't get dethroned because Kaelus announced his stance that he was against it and the other nobles backed down. Kaelus and Hes actually went to attica after her /self exit thoughts/ but before they left I think Heli and Hes had a conversation at the gardens (since Kaelus told the 2 that he almost lost his wife).

Due to political stuff, the 2 main couple come back to the capital to help Heli. Hes was very pregnant at that point.

Since the duke family now has an heir. Heli approached Diana to ask if she wanted to have kids to fulfill her role as crown princess or divorce. Heli doesn't want to force Diana to do anything she doesn't want. Diana rants how she became a scare crow crown princess. She had no power and just stayed at the palace. Diana chose divorce but she still continued to visit the Lion palace everyday because of the emperor (he wanted company). The nobles couldn't force themselves to offer other partners because Diana was still there and they thought they would get back together.

Diana and Hestia have one final conversation at the palace bench to close whatever relationship they had.

I forgot how the girl ended up getting chosen but she was sweet and respectful towards Hestia. She even wanted advice on how to have a partnership like hers. When Hestia's water broke they were actually together and she ended up panicking but helping as best as she could.

Heli and new girl end up havinf their own kids too. Forgot how many though

Oh so Heli had a new wife. Somehow I feel bad for Diana but at the same time I know that she deserves it.

It's his responsibility as the cp so he had to get remarried

Definitely, if only Diana just accepted her wrongdoings maybe she'll have a different ending...