Ancestor John Trumbull?

On my father's side of my family I am related to John Trumbull (the man who painted the picture of the Declaration of Independence). I am almost positive my dad said he is a uncle of grandfather (with a couple greats in front of course). But when I go to familysearch.org I can't see anyway that it could be possible. Apparently John Trumbull was an only child, as was his wife Sarah Hope Harvey Thurlow and they both never had children. Does familysearch.org have it wrong and maybe John Trumbull or his wife Sarah Hope Harvey Thurlow have at least one sibling with children and that is how I'm related? I'd really appreciate any help I can get with this. Thanks so much and have a great day!!