In worst cases the bloodline can still continue with his brother....
Or maybe make a baby using magic?
all his life the expectation has been put on HIM so ofc hes worried
Rather than being a bloodline-only thing tho, Urban is the *crown prince* and, therefore, the future emperor. That complicates things a whole lot more. He's socially expected to bring in a wife as empress and at the very least try to have a kid; while Kyle mentions that some countries seem to have male concubines for their emperors, the empress role would still be vacant... and also Urban's butler (?) seemed really against the idea, which might indicate that it's not something as culturally accepted by their country.
In any case, tho, Urban's parents probably aren't going to be against Urban taking Kyle as a prince consort instead and leaving things as is. His mom in specific seemed to be keen on Urban finding a "fated" pair instead of simply paoring him with someone who was politically advantageous, and then suspiciously stopped bothering him about it after meeting Kyle (not to mention she started teaching Urban some "wifely duties" lolol)-- and also Urban's dad is a big softie who is obviously going to be okay with things as long as his son is happy.
Their biggest social struggles will be the nobles around them and, most probably, Urban's brother (he didn't seem to like Kyle very much).
And other than that, the most prominent struggle is going to be between Urban and himself, both from the expectations he holds to himself as heir to the throne and the future he knows from his past life.
no one realising the 'im a guy' card actually makes SENSE bc he is a prince who is generally expected to continue the bloodline in a world where homosexuality doesnt seem that usual... let put our thinking caps on folks