I don't think waiting until 16 to date is harsh at all. That was the rule for my girls too. I agree with Allison--if he lives in your house, he lives by your rules. It's not right that his dad can try to be the "good" guy by disagreeing with you on this when it was the rule for the rest of your kids.

I agree with the others. Your rules are your rules, and if he knows this is a rule he can break, what other rules will he think he can break? You don't make rules for your kids because it is convenient for you (it's way easier to give them what they want), you make rules because you think it's in their best interest in the long run, to help mold them into caring, responsible adults with a bright future.