Similar to the question "How did Faramir know that Aragorn was the King in the Houses of Healing?". How was it verified that Aragorn was indeed the rightful king of Gondor and not an impostor. I.e., anybody could've walked into Gondor and claim they're the rightful king and here to claim their ancestral throne.
I assume that, contrary to the question I linked, it didn't suffice for a hobbit or even Gandalf to say "he's the king". Even ancestral records or a family tree, specially without e.g. DNA proof, should not be sufficient as anybody could say "Here are the records, I am Aragorn, I am the king".
So, how was it ensured that Aragorn was indeed who he claimed to be?