MM romance through POV of third character

Looking for a book about an MM romance (duh) between MC1 and MC2 but told through the eyes of someone else (MC3) who is not part of the romance (i.e., not MMM or poly), such as a friend or family member (but can be anyone).

To be clear, I’m not talking about third person POV (“MC1 walked across the room”) but instead MC3 observing the romance develop between MC1 and MC2.

If possible I’d like something written in the POV style of third person limited but I’ll take first person if that’s what you’ve got.

If anyone knows what this is called let me know!