But isn't he still a prince. If the emperor or empress were to find out, I think that there would be really heavy repercussions for the MC's family.
Exactly, that's why they can't just kill Perez right away and resorted to this nasty method.
No. The Empress will suspect them and it would become a problem. Also, he needs to stay there in order to still have his position as crown prince in the future. If he gets adopted, he won't be a valid heir to the throne anymore. Tia also needs to focus on getting the position as the head of her family, too. Tia still doesn't have the power or will to ask his grandfather something like that.
what if when tia comes back to her father and grandfather she asks them to adopt perez ٩(๑❛ᴗ❛๑)۶
that would solve a lot of their problems
but i don't know why the author wouldn't think of that and increase perezs pain ╥﹏╥