Some people of a certain ilk will say "don't look for trouble" or you just might find it. What does that tell you? Others may say "why get curious and ask or investigate if it will only ruin your life and bring heart-ache in the form of the relationship ending". These people think affairs are normal, natural, and unstoppable....and that its one's right to cheat on the other if and when they want to - as long as they "take care of business at home". Well, guess what? Inevitably, "business" doesn't get taken care of at home. The relationship or the family errodes. It is only a matter of time before the cheat gets bored and moves on to the next, too - if this is someone's pattern. There's no changing it. Some people aren't meant to be in stable relationships. Not ones of any substance, anyway.

thanks, but what type of friend are you?

Do you tell your friend their significant other was seen (by you) kissing another person?

Yes, if I was a good friend - of which I am....yes....I would find a considerate way of sharing this with them, especially if I knew they would want to know.

I'd tell them. I've been in that situation before...one of my friends husbands was cheating on her and I found out, actually saw them together holding hands and kissing.
It was hard, my friend got mad at me for awhile. But in the end she was glad I had told her.
I'd expect nothing less from any friend of mine.

If you saw your friends girlfriend/boyfriend kissing another person, do you tell? How would you handle it?

well id be sneaky and take a pic first,then id walk right up to my friends significant other and hit them right in the face.