Is your mom right if you like your stepbrother's friend because he treats you like an adult but your mom says it's just a school girl crush?

Many young people can form crushes on different guys (even older men) and particularly when they treat you as their equal. Yes, your nan and mom are correct, but, whether it be a crush or true love, it's important to you and shouldn't be taken lightly. It's OK to have a crush and you may have several before you find that right guy for you. For now, remain friends and perhaps when you are couple of years older your step-brother's friend may just ask you out. Miracles always happen.