Have you ever been attracted to a signifcant others sibling? Even just a little?

Okay, let me start by saying I never acted on it, but I was at a party last night and ran into an ex's brother and he was looking really good. We chatted a bit but that was all. It just got me thinking how cute I thought he was when I dated his brother. Like I said, I never acted on that attraction and I wouldn't ever, not even now, because I think that'd be rather mean, but I definitely find him cute. So, have you ever been attracted to someone you were datings sibling? Did you feel bad about it or just push it out of your mind and figure it was out of your control? I don't know why I wonder now, but like I said, the run-in has me wondering about it. Thanks. :)