Is it normal to to get turned on by the thought of incest?

Okay, basically I get really turned on by the thought of incest. I am 32 years old and I have never had sex with a woman, I still live at home and I have a sister and a brother, my sister still lives with my parents but my brother has moved out. At night I go in and watch her sleep and stoke her hair gently, I have also sat outside my parents bedroom door masturbating to the sound of them having sex and desperately wishing I could join in. The other day my mum told me to get the laundry bag and I smelt her clothes. My biggest fantasy is for myself, both my siblings and my parents to have sex all together but I don't know how to ask them, I would love for my mum to take my virginity she is a lovely woman. I know people will think it's sick but is there anything actually wrong with it?