Does the past matter?

Tee. 🌸 • A college student striving for greatness!
So I've been talking to this guy for 3 months and we've finally started letting our family members know about each other. I'm 18, he's 18. 
Last year (Junior Year) he got into some trouble with marijuana. His friend gave it to him to pass on and he got caught. Now the principals at the school can vouch for him being a good kid and the past not affecting the present. My grandmother works for the school and my dad is saying he's going to have her look him up. 
I told her that wasn't fair for her to look through his personal information just S cause he's talking to me! I'm afraid that they're going to make me stop talking to him. He isn't a bad kid. He's a good boy. He looks like a bad boy but there's so much more than meets the eye. 
Any advice?