Do breeding, adoption and marriage proposals really depend on number of regions owned

Well, some folks in this and other forums say that breeding, adoption and marriage proposals are directly connected with the number of region the player holds.

According to this, children are only born and adoptions and marriages are only offered when your number of family members is below a certain threshold. This threshold is a ratio to your regions (some say 1:1, other 1:2).

However, this seems not be true for the man of the hour promotions - these can happen any time.

Still, I wonder if this threshold-hypothesis is really true! It does't seem to make sense, as wasting your generals left and right will always get you new ones, while conserving them by using them wisely is a waste of time, because you would be unable to increase the total number of generals that way.

Furthermore I wonder about the use of the fertility trait. A chance for more children would be negated by a threshold.

Yes, the number of generals is capped and closely related to province number. In several hotseats so far we've had one faction grow large and adopt a dozen or so generals, making adoptions for other factions impossible (mysterious death event). MOTH promotions are separate and are uncapped as far as I know.

Conserving your leaders makes sense if you want a 10 chiv general with governing traits/ancillaries to pop boom a city. Or in the Stainless Steel mod, where the royal line is separated by traits from adopted pretenders.

Furthermore, adopting generals makes your existing royal family gain negative traits like anger. Gaining children is different from adopting generals - if you already have them they will mature when the time comes. You have a higher chance for offspring when you have a low number of FM's compared to your province count, but I think you can still have children even if adoptions are no longer offered or possible. The cap of 4 children per pair of parents is hardcoded.

I seem to have the habit of using the adopted generals as cannon fodder. As it doesn't matter to me when they are killed in battle as they aren't part of the main line anyway. That's probably why the tree for me ends up looking like an Age of empires tech tree but anywho, i did notice that above part is true. Ironically, i'm very safe with the blood-related heirs.

The family tree hard cap based on the number of provinces always bothered me on that. But it's never become so much of an issue that i run out of blood relatives.

Some factions have a hard time. It's easy to have trouble finding husbands for your princesses as Spain due to a lack of provinces. I usually have one marry the unrelated general you're given. Venice can also have a hard time, as, if you aren't expanding you'll soon be overwhelmed with a flood of sons. But yes, your generals will refuse to have kids if you don't have enough provinces. It's really weird...

That's why it's best to keep the family streamlined, room to grow.