@jym626, I think Belgium is east of France or something. I guess that makes it “Eastern European”? (just pulling your chain).
I just wanted to repeat that I am not making a value judgment about what the friend SHOULD do, simply trying to answer the OP’s question about what the friend is within his rights doing.
There are people who live among Native Americans and identify as such, participating fully in cultural events, but who cannot legally prove lineage, and thus cannot claim it officially. Life is unfair in both negative and positive ways.
Why your kids are not proud of their Japanese heritage is a bit of a mystery, but it really is a personal choice and has no bearing on OP’s friend’s “Hispanicity”.