crusader-kings-3
Feasts will often have events which give you choices which will either increase or decrease the opinion of every guest. That's all fine and dandy, but it be great if I could know exactly who's at the feast when I'm presented with these decisions, since there's some folks whose opinion is already so high that I don't really care about taking a small opinion penalty.
How can I see who the guests are at a feast?
I stumbled upon this entry from the CKIII FAQ posted by Paradox themselves:
Q: I understand that the head of the most powerful house head becomes the head of the dynasty, but what determines who is the most powerful house head? Which factors are the most relevant?
A: Military strength is the main factor
But it appears that when the head of the dynasty dies, then the new head is determined before the titles of the old head get passed on the heirs. As your primary heir will usually not have that many titles and vassals at that point, the head of the house title will often pass on to a different ruler of your dynasty.
Fortunately, that's only temporary. A couple months later, the game will reevaluate the military strength of all dynasty members, see that your character now has all those troops from the inherited titles and vassals, and give the head position to the now strongest character (you).
Two characters are considered related for the sake of the inbreeding warning if they share a common ancestor up to their grand-grand-parents. So you should look at the character screens of the four parents and see if their parents and grandparents look similar. When there are any people listed on both sides (not necessarily in the same generation!), the game considers the characters related.
For example, the grandparents of the left person are the grand-grand parents of the right person:
In this case I am looking at the character screens of their respective mothers, but to make sure you would also need to compare the fathers side and each others father with each others mother. A convenient way to perform that comparison is to temporarily "pin" those 4 characters (icon in the upper right corner of the interaction menu). You now have them in the outliner and can switch between them with a single click.
But keep in mind that the fatherhood information you see on the character screens is the official version. When you let your spymaster spend a while "finding secrets" in various courts, you will notice just how frequent adultery is in the game. While the motherhood is reliable (at least I did not discover any "switched at birth" scenarios yet), the fatherhood information should be seen with a grain of salt. So "They are related" should be read as "They appear to be related". This of course can also mean the opposite: When two characters share a male ancestor due to an affair and your character does not know that, then the game won't give you a warning.
Best Answer
This is super unintuitive, but when you host a feast, a little tiny feast icon generates on the map when you're zoomed in close enough. I think it's always in your capital when you host it, but if you get invited to a vassal's feast, it'll be in their capital instead.
When you click it, you get a nifty little pop-up with a list of all the persons attending!
Hunts and pilgrimages also generate a tiny location-specific icon, but I don't think those expand out to show who's with you. (This may be a bug)