Is it normal to have these fantasies?

When I was 12, my brother (12) and my sister (11) were always on the Internet. We would go on omegle and there would be people you know touching themselves. We wanted to see how it felt so we tried it too. We would hide under my brother's bed so no one would find us and my sister and me would play with ourselves while my brother had his penis out and would moan to turn us on. Whenever i wanted something he would tell me to give him a handjob. At the time he didnt know what it was called. Being only 12 none of us knew what we were doing. We had no idea it was basically incest and not acceptable at all. And that lasted a little while and now we never talk about it again. But sometimes I think about touching his penis again or touching my sister's vagina and I don't know if this is just a fantasy because when Im not turned on, I think about how wrong it is to think of that. Is it normal to have those fantasies?