I started with another site called FamilySearch. It's a repository and links to other repositories for various records such as census, birth, death, probate, military service, marriage, tax and land records - and more. FindAGrave is just one of the sources FS gathers records from. The memorials are largely based on physical headstones and/or cemetery burial records. It isn't 100% error free but keep in mind many of these contributors are very dedicated and serious about what they do. The person that created this memorial created 4,000+ over nearly 13 years and maintains over 5,000.

I do find the date of creation interesting, that it was done so soon after we started learning about Jr. Is the contributor (Mr Isbell) one of us, looking into the family and posting it up because that's what he does anyway or putting fake info up to help Podesta? It is a rather sparse record and Mr Isbell isn't even sure which cemetery he's in, so no plot number or headstone photo. Not knowing the cemetery isn't unheard of, I've seen it before.

I'm not questioning the entry itself. I'm sure it's as accurate as it can be. I believe the contributor welcomes questions, so if you wanted to now how he came by his information I'm sure he'd let you know.

TL;DR - You can generally trust FindAGrave's information. (I find more errors in "official" records)

For your actually question - There's always the possibility Sr isn't Jr's real father. After all only the mother is known for sure, particularly back then - no dna testing. These census, death and burial records aren't usually going to out an affair - or elite sex parties. The resemblances are uncanny, though. Freaky even.

I have thoughts/questions about Sr & his father from what little I've seen but does this post really need to be any longer?

I just wanted to give you more (and full) names to work with and those birth and death dates can be helpful.