Created a tracking system for bastards, but it can stand on it's own so I released it as it's own mod, called Bastard Ledger if you're interested. Will keep track of all your illegitimate offspring so you can view them later, can use on existing save games.

@Zeiaxar thanks, I did find a few problems with the revelation aspect of the kids.
Fixed a few things there, hopefully solving your issue. I never used it for my own kids, thanks for testing :)

This mod is 100% compatible with everything - the only issue we would have with other mods, major overhaul mods included like AGOT, would be the suspicion of the husband - if they use the file pregnancy_events.txt
Our mod here removes that suspicion, and the AGOT compatch removes it for AGOT.
Otherwise the husband, based on his skills - intrigue probably? might suspect something and confront or investigate the wife - again outcome based on skill levels, possibly resulting in her death/exile for being a cheating *****. Not intended with this mod so that's why we change it.

Testing it with Agot, Agot+, and Legacy of Valyria (plus compatches), and not sure if one of them or all of them don't like this mod, but for whatever reason if you don't immediately choose to reveal the parentage in one of the two ways to do so when the child is born, choosing to reveal it later via the decision and the like does not work at all. You click it and it literally does nothing, despite acting like it was clicked.

@eridano2013 in real life? good for them lol
Unfortunately with this type of thing the vanilla game would treat the females as the perpetrator - fornicator/adulterer etc. and most religions view female infidelity as criminal - instantly jailing their spouse on discovery and either divorcing/killing/exiling.
That's pretty harsh for this mod, so instead we just remove the husband suspicion that the base game has.

Thanks for the detailed explanation, I'll use your mod!

I asked because here in Italy, there are many legends about female subjects claimed by the lord, who sometimes incited peasant revolts or killed him with a dagger.

@Eridano2013 for you personally there are no consequences unless you actively choose them.
On birth of a child you get notified and can choose to keep the secret, if you don't reveal it the husband will think it's his and carry on as normal.
There are secrets, you are the "real" father, so whatever mechanics are in place for the vanilla game are valid for discovery - however the husband will not be suspicious and never confront the wife.
As for who you decide to use this on, that's up to you as well in the decision/law - four selections from just your court/guests to ALL marriages in the realm. Also when the event actually fires on a new marriage, you can choose to do it or not.

I would like to know if the "Jus" requirement has consequences for the attitude of me, those involved and their families (e.g.,pride, self-esteem, jealousy and feelings of revenge, attempted revolts, plots, etc.), and whether the "Jus" is limited to non-nobles, or is it also exercised against nobles and vassals (more dangerous), and with what consequences, if any. Thank you.

bro makes some of the best mods

@10k lol enjoy :)

truly a mod i never knew i needed but am so grateful for

Not very enthusiastic about poe2 update so I'll be testing this more this week, seemingly everything is working great and nothing showing in error or debug logs at the moment.

Created compatch for AGOT:
https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=3557254933

@HeirandtheSpare I didn't claim this was historical and it's certainly a fun flavor mod, try it out :)

@HeirandtheSpare u think no king or ruler ever thought of this?

yeah it works you just have to wait 16 in game years for the secret to come out

Is this still working? Ive activated this in a few of my agot playthroughs but no events pop.

I think when I marry someone matrilinially the event wont fire. When I marry someone patrilinially the event fire as intended. Maybe I missed something..

Can you make a gamerule so we can select if AI by default won't do it?

Remember, you can't say this was medieval, because they absolutely despised it. I bet this would happen, like Stylez said below me, in the "Song of Ice and Fire" Mod.

@BirdHub19 100% lore correct For AGOT-ASOIAF

Alrighty, final update done unless paradox changes game code that effects spouses.
Working - added picture that shows event.
Might add option to not enforce your GOD given right, if people want that.
Like if your friend gets married and you don't want to .. enjoy.. his new wife. It adds a positive opinion modifier to the husband and wife, and nobody knows it's your kid unless you reveal it, so, not really needed imo. Plow away.