I Don't Know How Old The Boy Is
But there are several things to keep in mind.
In some parts of the world, including Europe, the age of consent is a lot younger than 18. Sometimes 16. Sometimes 15. This movie was not made in the US.
The second thing is that "Lolita" and the remake were made in the US and it was a teenager and an older guy.
OH, that was a teenaged GIRL and that makes everything more acceptable, right?
You also don't know how old this boy really is, he may just look younger and can play a younger teenager.
Just be honest and admit that if this was about a teenaged girl having a relationship with a young soldier around Walt's age - between 18-20, you wouldn't even bat an eyelash.
You have double standards when it comes to gay sex. There, isn't that better.