I'm 20 and a transwoman (pre-everything) and I came out to my brother, 13, on the 25th (automod's an arsehole), which my parents are very angry with me for. 

I discovered I was trans about 5 months ago, and have been open with my parents the majority of that time (I live at home still), but have still been living as male because I have no idea how to begin to approach that with them and ask for them to call me Kira and refer to me as a girl (as much as I really want to).

On the 25th we had my grandparents over, they are super homophobic, racist, sexist, the whole nine yards, so they don't know that I'm bisexual. I was in the kitchen with my brother (I'd had a few drinks so I was more loose lipped than normal), and it came up in a chat that they didn't know I was bi. I jokingly said "There's much worse things that they could find out about me", he replied that he thought he knew what it was. I asked him if it began with a T and he nodded. I told him everything and he seemed very okay with it (there was the whole "you'll still always be my brother not my sister" but I can work on that one), and we had a very nice chat about it. 

I later told my parents that I told him and later that day my dad told me that I shouldn't talk to him about it again. He says it's far too much for a 13 year old to understand and that I'm putting a lot of stress on him by telling him. My brother is absolutely fine and doesn't seem phased at all by any of it.

Is what I did wrong? Is that too much for a 13 year old?