oh it’s chinese slang! 贴贴 literally means to stick together but colloquially/on the internet it has more the connotation of snuggling/cuddling. you’ll see it used with cute emojis or gifs of animals rubbing their faces together haha

in terms of how it’s related to haobin there was a bts video from the bp tomboy episode where hanbin goes up to hao and rubs their cheeks together lmao — here’s a link https://www.tiktok.com/t/ZTLY2hhwC/