LOL wut?! If you had reading comprehension you'll read tht the ML knew MC had visions but only saw MC as a BROTHER for years until the MC was older and started dating and suddenly he felt jealous, and he had to work through why.
Grooming is when you take a child, give them love and gifts and tell them it's okay to touch their no no square since it's a special relationship between just them. Which the ML never ever did, he cared about MC as a brother growing up and is 10 years older. So once the ML was older he started to realize what he felt was a connection to MC, they were souls who were connected.
I'm not making excuses at all, I just know how to fucking read.
I dated someone who was 19 years older than me. Soo yeah an adult can make their own choices, and no grooming happened. Just say you're uncomfortable with age gaps that's fine, but calling something grooming when it's not isn't going to suddenly make you right.
Move on from the story and enjoy reading something else.
Bruh. If you're uncomfortable both age gaps then be uncomfortable but use grooming in the right context. Grooming is not just knowing the child, it's lusting for the child, manipulating/training the child to like the person, and waiting to get them at the right age. Hence, the word grooming was coined. There is an intention from the get go to have a sexual and romantic relationship.
There isn't here.

So this is just a story about grooming? :/