Well, I like guides and working on them, so maybe I've found the first to tackle. I was poking around the text files last night and found the fertile traits in one temple (not sure if it was love or healing or both) and the doctor, physician, wise woman and witch as ancilliaries. Those are split between the healing temples and the academy lines (not sure how many of the academy ancilliaries the nomads and barbs can get from captured buildings either).

But none of those explain what I saw (which is only a few data points though, so may be as much randomness as real data). I had a small baby boom, but not clearly tied to the ancilliaries I did get. And I didn't luck into any fertile trait itself. My territory count was 3 for most of that dead stretch. Then I saw a couple babies and 3 more pretty quickly after I captured the fourth.

It could be a combination of territorial expansion and some help from the two ancilliaries that were there in 2 of the cases. And, of course, random chance.

I've just seen LONG dead periods when trying to succeed with Sarmies. I don't yet have much experience with the other BI (or for that matter RTW, though there are quite possibly differences both due to hordes and other factors) factions so was curious if it's the norm or unusual.

The BI temples are refered to by generic names ("temple of horse," etc) in the game files, but but diety names in game, so they have to be correlated before they are really useful while playing.