What sort of proof is that? I repeat I have never observed my great-grandfather.
Plus your "definition" of information is pretty useless. Its seems a conclusion using your premise is that outside of a specific mind being discussed there is no information. And it would seem that this is not information
There is no information there unless there is a mind that can see it and make sense of it.
Similarly, there is no “information” in DNA absent a ribosome and tRNAs that can “decode” and “translate” an otherwise meaningless sequence of nucleic acids into a functional sequence of amino acids.
The only definition of "information" in play here is that it is an abstraction, which you've already agreed to. It is a mental construct, and it is "information" within any mind that can comprehend it and use it to make that construction. Before that happened, it was not "information".
What is the significance of you never having observed your great-grandfather?