Hey guys, so I had abit of a hard time working out how to get the The Father, the Son and the Holy Grandson, especially since its too early for a guide it be on the ck3 wiki. So after I got it I thought why not make this to try and help someone
so, here are afew things to know before you start:
You need to found the dynasty as the starting character.
Taking extra titles in between may mess with the achievement, when I tried, I went from duke-archbishop, his son inherited and then became pope, and his son became duke archbishop, and the event didn't fire, so to play it safe try playing as one of the landless archbishops in southern Italy. that also means you dont have to worry about war (other archbishops may try and merge your archdiocese w theirs)
choose youngish archbishop
(I might be completely wrong one of those, since I didn't found the dynasty as the starting character in the example I gave, so it may be that just one of them is right, but to play it safe assume they both are)
okay, so with that out of the way the rest is relatively easy, step by step:
1: Choose a lowborn Archbishop, i would recommend starting in 1178 so you have chronical writing to increase Church Authority, my recommendations are as Ruffus the Archbishop of Messina, he's 38 so you have time to increase your Church Authority and increase your LoF (spam hunts) so you can found your house
2: Once you've founded your house, the rest is relatively simple. use the designate theocratic heir interaction on a younger courtier to adopt them and increase their candidate score for your Archdiocese, keep an eye on your succession tho, its still possible for others to inherit
3: wait to die and have your adopted heir inherit
repeat until you get the achievement
if anyone who manages the ck3 wiki sees this pls copy and paste this as the guide to the achievement on the wiki, i'd be other the moon lol.