And I knew a guy who was girl crazy in elementary school. He had a girlfriend for a couple of years and even got in big trouble and was suspended for touching her inappropriately under the parachute in gym class.I dont find it hard to believe that a 9 year old may very well know they are gay. Children start mimicking relationships as young as 5, finding others attractive even at those young ages, without any thoughts about sex at all. It is adults who link sexuality to sexual activity. My son had a girl friend in 2nd/3rd grade. I had a boyfriend in 1st grade and crushes on two boys in 4th grade (8/9 years old).
Like you, he "knew" he was heterosexual at a very early age. He is now married to a man.
There is know way to know if a 9 year old child "knows" he's gay - and certainly no way for his parents to "know" that he "knows". That's way too strong of a word.