Accidentally starting something

Reposting as this got removed before for some reason.

So I know technically not incest but as close as for me (33M). My wife (33F) has the hottest little sister (25F) and she is basically a sister to me having know her for 16 years.

Anyway for like the last 5 years she was really turned into a fantasy / desire of mine. I have often enjoyed my wife imaging it was her sister and enjoyed watching her is tight jeans / swimming outfits etc.

Anyway this last week we went to stay with said sister at her apartment and at some point wife and sister went out so I was left in her apartment alone, I certainly enjoy her underwear draw, basically dipping my cock into a pile of used panties, finding her sexiest thong and wrapping it around me while I cam onto her pillow...

So lets say I was a horny beast now and the next day my wife goes to see some friends so just her sister and me in apartment, I am lying on sofa and sister lies down at other end and bends so her ass is looking fantastic in jeans, I keep imagining which of the panties I rubbed my cock on the day before she is wearing, cleary hard as a rock staring at her ass I don't notice she has seen me and goes 'like the view'. I just laugh it off but she goes I dontine the view either as she clearly is staring at me crotch.

She starts rubbing my legs with her feet and I see her starting to undo her jeans but we hear my wife's car come back and she suddenly stops and runs to her room...

We haven't been along since but fuck I am excited for next time we are.