Is it normal that i masterbate to my thoughts of my sister

Since you already masturbate to thoughts of her, then start masturbating where and when she can "accidentally" catch a glimpse of you pleasuring yourself while saying her name.

Spend more time with and around her. You'll get better looks, at least bikini or partially naked, if not fully naked, as she gets more comfortable with you. Them, it's cell pics, poses, and fun playing around. It will become your regular thing together.

In my case, I had a thing/fetish for my hot older sister's body and long, always polished nails (as did she..her nails were and are our shared thing), and would pose them to her skin and take pics. That soon became a fun "hey, how about a little lower" or "open up a little more", pressing her nails against her tits, bare tummy, and into her thong undies..Which then became, hey, why don't we do a little photo shoot thing, just between us? I had hundreds of her..Maybe more than that.

Stop the fucking around
Ram your cock into the beautiful wet pussy of the dirty cunt
That will stop all thoughts of masturbating to thoughts of the fuckin whore

I don't personally find it very normal, no. And I don't think the vast majority of society does, either

I have thought of that, but not sure if she would go for it or not. Would you like if your brother tried to get with you? Wondering how common this is.