Kira & O’Brien should have told Keiko they were starting to develop feelings for each other & didn’t want to risk it.

Either Keiko would have been okay with them keeping their distance & would have been mature enough to understand they are both fighting their feelings OR she might have encouraged them to indulge, she did tease him about flirting with the jumja stick vendor so it wouldn’t be completely out of character for her & we could have had throuple representation on Star Trek.