fr
There is only an 8 year age difference.
The uncle was 13 when he started to train the 5 year old prince.
That is what the summary says on MangaUpdates.
Only? That's a grooming age difference
When could that be done? There were servants around them nearly all the time.
The young prince is usually sick and weak, and as such is watched constantly. But kept away from people his own age that could become friends.
The uncle never laid hands on him. He fled and got married.
They were kept apart for years.
For whatever reason, the young prince has always wanted him. And the uncle realizing this quickly got married and restricted his contact with the prince.
But as the prince became an adult, facing permanent separation, and the prince pursuing another man...the uncle seems to want to stop denying things.
That doesn't sound like grooming. Grooming is different. Grooming is intentional manipulation to knowingly seduce someone into your way of thinking and behavior for malicious purposes without them being aware they are near a predator.
And this situation, even with the incest, doesn't feel like that.
The uncle and the prince are the endgame happy ending.
If you don't like the story, just drop it.
I am absolutely not convinced mc wasn't at least a little groomed