>sister and me used to casually walk in on each other in the bathroom. Say sorry to each other, took what we needed and go out.
> me coming out of the shower once. Towel around my waist. Sister walks in says she needs to brush her teeth. I said yeah I’m done with my stuff.
> walk in and out of the door at the same time.
> both turns sideway to walk past each other.
> my dick rubs past her ass. I could feel the two bumps. Instant erection.
> try to quickly move away.
> she has a surprised happy face as she looks at me.
> I apologies. She says not to worry as it happens.