I don't know if you can judge him from something he did at 15 At least not if it is an isolated incident. God only knows what regrets we all have. People grow and mature and change. Now I do agree the inappropriate touching is concerning. As your partner he has to respect you. I don't think you can connect the dots as a pattern unless there are other incidents but him touching against your wishes is not appropriate. You need to firmly to tell him to stop, that it makes you uncomfortable, but you have to be willing to follow through if he further continues to not respect your boundaries. If he sees you as an equal partner and someone he wants to spend his life with he will stop. You're not comfortable with it is the only thing that matters.