We standardized for parts, ammo commonality, and interoperability.
Every adult in the immediate family has a SBR'd 5.56 10.5" AR-type carbine, a 7.62 16" AR-type carbine, a Benelli M3, a Glock 19, and an Omega 36M that can be used on everything but the shotgun. There are two MRADs with .308 and .338LM kits at different locations, and the Omega 36M works on those as well.
We also decided to leverage the AR-15 platform's modularity; every 5.56 carbine also has a 16" upper and we have three CMMG Banshee 100 .22LR uppers at different locations.
And plenty of parts.