Most Helpful Girl
I think it would be best if your ex tried to stop getting involved in yours and your new boyfriends business. I really think he's just trying to stick his nose in. If he wanted to sort things out with you he'd speak directly to you. Since him and your current don't know each other the f/r is sort of unnecessary without there being another reason.
The other side could be he's they kind of guy who just adds everyone and wasn't thinking about you too much when he sent the request. However given the history and present, i doubt he'd be socially unaware enough to send a request to his ex's new guy and think nothing of it.