I don't say anything about male pregnancy being common. But it's not entirely unexpected, since it's happened before.
Being locked up while pregnant doesn't mean the brother will let him starve or anything???? It just so uke doesn't run around so freely bcs he already got kidnapped twice. And bcs his family and the emperor's family has this rivalry setting towards each other, it's obvious he doesn't like the idea of his brother got knocked up by the emperor.
"It's his body what his fuckass crazy brother do with it" bruh do you even have an older sibling??? The brother perceives his brother as this innocent kind but clueless little brother that will easily get swayed by others. To get pregnant outside marriage (moreover bcs he's a pope), and by rival family at that, ofc the older brother instinctively become protective and angry. This protectiveness is something common for siblings (if u r close to ur sibling), whether u r in love or not

?? hes a pregnant adult chaining up the door locking him in a room grounding him not allowing him to see the other father when hes almost due after the emperor already missed majority of his pregnancy ?? let them have some relief and me some cute moments . irritating