“only imbeciles want credit for the achievements of their ancestors”. What does this phrase means?

Here’s a great example. My brother, who was kicked out of the military on a hardship discharge for being lazy, takes the years and credit of medals and accomplishments of our grandparents as his own. He tells his wife that he was a P.O.W. and a Green Beret. He’s definitely not a Green Beret.

it means only idiots fall back on the achievements of those who came before them, because they have none of their own.