Brother Showing Me

This happened when I was 13 and my brother 15. We had gone for a swim and then made a hot bath for after the swim. We both got in with our pants on, and one thing lead to another and we were showing each other our dicks. We giggled when we saw each others as his was hairy and mine not. He then asked if I had ever had a stiffie. I lied and said no, what's that. He told me that a stiffie was when your dick filled with cum to make it hard. I asked what cum was, so he started wanking his dick and after a few minutes of this white stuff came out the top of it. It has never happened again but he has caught me a few times.