Lovebuckets, we're not ALL engineers, some of us work in IT!
He does sound like he could be on the spectrum, based on my own experiences. Doesn't mean he doesn't care for you, but probably doesn't even think to hug you.
My son was like this, he'd be hugely affectionate to family members, but not to anyone else. And his parents might be completely unaware of it because he is fine at home. We only became aware when the school raised with us how he was at school.
You COULD raise it with his parents, but I'd be very careful how you did it, its not an easy thing to hear!
You could try reading him social stories, ones that involve hugging people, social contact. If he IS on the spectrum, he needs to learn social skills, they don't come naturally, and you'd be doing him a BIG favour!
(my DS and I both have Asperger's btw, I was dx'd after my son)