I seem to bump into the same dad from my kids school all the time, and he's gotten very chatty and friendly towards me. It's never been flirty just very friendly and I thought it was sort of built rapport from happening to bump into him so frequently. Except the friendlier he's gotten when alone has made it all the more obvious how he completely blanks my existence when he's with his wife. If he drives past me alone he waves, he drives past with her he looks dead forwards and doesn't so much as smile, if he's alone and is ahead he will hang back so we walk to/from the school chatting but if he's with his wife we can be literally walking up the path almost next to each other and he won't look in my direction whatsoever. It's made me not want to acknowledge him when he is alone! It's such an odd thing to do, isn't it?!