The last part of the movie made me cry :(

That is the impression I got also. He couldn't have children at his age to carry on the line and the heritage.

Part of me wondered if he was ashamed because his lineage was made by a fling whereas Ralph's grandparents seemed to be a little more of a loving relationship. Or perhaps he was implying the maid was molested by his great-grandfather but they only hinted at it being a PG movie, and he would have felt ashamed to ascend to the throne as a result of that. Men typically don't like important female figures in their life being wronged by men, even if the person is also family.

One thing I'm also questioning is why he would insist on a non-American who's an embarrassment to him when he has to know his circumstance would be forgiven once they know his character and that it might ultimately be better for the country if he went ahead and took that risk. I know he swore Duncan to secrecy but that could have just meant in front of Ralph, because all those researchers ultimately would have found out he was in the running so I'm assuming he informed the entire room of his declining the throne and was seeking out the next in line. It got me thinking that maybe because he had just lost so many family members, he decided to look out for family. Given Ralph's struggles and background it might make sense that he'd wish to coach him along since they're fairly equal in relation to the monarchy. I know it's "just" a comedy but collectively they're defending the family legacy, something we all want to do but in their case it's like the ultimate version of it. Goodman is in fact young enough to be his son so it could have been his way of finally getting to experience being a father in a way.

I feel like I'm forgetting a detail but I think it's pretty much all been said. One thing I'm curious about though is how exactly they're related. I'm guessing Cedric's great-grandfather is a great uncle to Ralph's grandfather, being that their connection to the family is paternal and they're from the same line. It's possible Ralph's grandfather is one of Cedric's uncles if I'm doing this right:

Ced is a generation older than Ralph therefore one generation younger than Ralph's grandfather, who himself would be another generation younger than Cedric's GG. However, if these hookups happened when the men were young/old, it throws off the whole thing!