Is it normal that i have urges to do things to my family?

I had a dream last night, where I was 'doing it' and my whole family walked in. My brother and farther got naked and joined in. The other guy went away and it was just us three. Mum then got undressed and joined in too. I woke up and I was wet, and now I'm worried. I can't stop staring at my mother, who I imagine naked all the time. My brother is the same, but my farther, not so much. I just imagine a little of him naked. And from what I've imagined, he's hung.