@shikaka I am wondering have you ever encounter the situation that when you use your companions as lords, the number of troop in their castles just won't increase in a long time? and the same thing happens after AI take a castle. It's just pretty wired that the troop in castle juat remain at 30 or 40 so that I have to recruit them mostly myself, shouldn't the AI recruit troop in castle automatically? If you have any idea how to fix it, I'll be very appreciated.
This happens to me, but I usually don't care about it much.
I usually form my own faction exactly once in every mod (just to prove that I can do it), but I don't enjoy playing a ruler much. Most of the time I take a city and it's surrounding villages for myself, and don't really care about getting more fiefs.
To answer your question, I see that lords (not just companion lords) don't increase the garrison of the cities for quite some time. If you care to keep it, you have to defend it in person. Since I am a vassal most of the time, I usually don't bother doing this, there is a considerable yo-yo effect in play: the same castles changes hands very frequently.
I think the current garrison setup is similar to native. But it works less well, when the enemy factions have more lords with big armies (lords have 2000+ renown, so high in numbers)