You just had knee surgery and you can't walk so you've been laying in bed. Your sis comes in to check on you. She asks if you could get up really fast if you wanted to and you said, no of course not. She keeps touching your leg brace until she reaches all the way up your leg to your dick. You tell her to stop and that she's your sis. You can't really move to stop her so when she starts sucking your dick. You can't help but to get hard. Next thing you know, your sis is riding your dick and you're cumming inside of her.