Would you tell your spouse

I would hope that a sibling would not be making a pass at me. If it were my mates sibling, then yes, I certainly would bring it up as soon as the opportunity was there to do so. I would not leave it for them to find out later. As this could give the wrong impression. If a friend of ours made a pass at me, I would confront the friend immediately and in no uncertain terms. I would also share the information with my spouse as soon as time allowed. I would tell my spouse immediately, as soon as time allowed.

Yes, Do not keep anything between you and your spouse.

Yes, indeed I would tell him and I would want him to tell me too. The thought of keeping it from him would be written all over my face and I'm sure I wouldn't be comfortable being left with the person and sooner or later he'd notice anyway, so why not tell him out right. But the main complication this way is that he might go and kick someone's a$$ for doing that to me and thus, friendship or family bond could be ruined. I guess I won't tell him right then and there but first check his mood and if I could talk to him nicely, perhaps he'll let it go but he'll be conscious not to leave me alone with the guy or the friend since I don't feel safe. The point of it all is, test the waters first before talking to guy. Unless you want broken bones or bloody encounters ~ which I'm not a fan of.