I've seen too. He is Keith's mom, the whitegray hair guys. If you want to read in advance search the page Yaoi Memes for Everyone in Facebook though its fanmade translation but still can understand.
Apparently back in the middle ages in german, kissing someone on the lips was normal and sometimes used a sign of gratitude and manners so I guess since its keith's mother I don't think theres a problem with that considering it could be an act of proper manners
I don't know why they kissed.