Tell them honestly, kindly, and directly.
“I love you both and I wanted to be honest with you. I’ve started dating a boy, and I want to tell you about him.”
“I know you’re worried about me dating because you don’t think I’m old enough, but I wanted to tell you that I do have a boyfriend. He’s awesome, and I really want to talk to you about him.”
Give them reasons why you think it’s OK for you to date.
“You’ve told me that you don’t think I’m mature enough to have a boyfriend, but I’ve shown that I’m able to keep up my grades at school and all my extracurriculars on my own, and I think that’s a sign that I’m mature enough to make my own decision in this.”
“I know you didn’t want me to date anyone in high school because I’ll be moving away soon. But both me and him both know that going in, and are OK with it. We can be adults about it, which is why I’d really like you to try and accept this.”
Tell them a little about your boyfriend.
“He’s a really great guy. He’s really close to his family too, and he’s at the top of our math class. He’s actually been helping me with some of the harder chapters.”
“Here, I can show you a picture of him. He volunteers at the dog shelter and he’s on the swim team. He’s really nice, and I think you’d like him a lot.”
Offer to make a compromise if your parents are uncomfortable with you dating.
“I’m willing to compromise to make this something you guys are comfortable with. We can agree to only go on dates in groups of people, or something like that.”
“If it would make you more comfortable, I can just see him at school instead of going on dates.”
Give them some time to come around to the idea of you dating.
“I know this might be kind of surprising. It’s OK if you need some time to think about it more.”
“Thanks for listening and being open to this. Can we talk again tomorrow, or some other time soon?”