
Could it be that she got pregnant with Mars babies and the current descendants of the royal family are his and not the king or emperor?

If that’s true, than maybe Mariana wasn’t the one to kill Mars but her husband, the previous Emperor. He probably didn’t know about her being pregnant with Mars’s child, but knows they were lovers. She just sees it as her killing Mars because she thinks it’s her fault that he died.
I’m guessing Mariana didn’t have a choice when it came to her marriage. Her parents probably forced her to marry the Emperor. Mars was a hero, but did he have any noble title. I think he was a commoner (I could be wrong). In her time, status would have been everything, especially if she’s from a high ranking noble family. Also we don’t know exactly when he became a hero, was it before her marriage or after her marriage.
Poor Jeno, he’s in delulu land rn. He can’t believe his idol would died like that.

Even if this theory is near from the truth, shouldn't Marianna just forgot about Mars cuz she's already married?
This is just the problem with nobles and aristocrats (in stories) they see mistresses and side lovers as a common thing and not a bad thing. I understand that maybe they really lobed each other but girl is already married. Mars is just blinded by love.

But tbh, if I'm right, I think having mistresses and lovers during the aristocratic period was actually common but it's more so for the wealthy and powerful. Doesn't mean it was normalised within their "high society" but it was common and supposedly if they do have a lover outside, they are supposed to keep it discreet.

Especially since at the time main priorities are having influential relationships, status, wealth and heirs (still important today). Having mistresses meaning chances of having children (illegitimate yes). Off chance children with the main wife doesn’t work out, but can’t get divorce the wife (either because the wife’s family is powerful/wealthy or divorce is not a thing at that time), having illegitimate children means having someone to continue the family bloodline. Tho illegitimate children will be looked down upon, would be considered inferior to legitimate children. Having mistresses also means having connections to their families as well.
Did he have a growth spurt??
More like he transformed after suppressing his growth haha