AU where Leia, Luke, and Han snuff out the First Order 20 years prior to TFA. In so doing they rescue the kidnapped children the FO was going to train up as troopers too. Leia and Han adopt baby Finn, giving Ben the sacred duty of big brother.
20 years later, Ben still takes that responsibility VERY SERIOUSLY, which is why he is doing everything in his power (FORCE POWERS INCLUDED) to keep his brother and Poe Dameron apart. Ben knows Poe's reputation as a notorious flirt and shameless rake. (Little does he know his precious, flawless little brother Finn is the one doing the actual chasing here.)
Poe/Finn - No FO AU
20 years later, Ben still takes that responsibility VERY SERIOUSLY, which is why he is doing everything in his power (FORCE POWERS INCLUDED) to keep his brother and Poe Dameron apart. Ben knows Poe's reputation as a notorious flirt and shameless rake. (Little does he know his precious, flawless little brother Finn is the one doing the actual chasing here.)