Nope, he isn't. The grandfather on the family tree doesn't have a mustache or thick eyebrows -- although he DOES have goggles. It's a little puzzling.
Most likely the author didn't know about that iteration of Goofy's grandfather. I'm actually surprised he used a direct relative instead of Yet-Another-Uncle
At any rate, who is the story by? I love its version of Young Goofy, and the grandfather character is interesting. That being said, and even though I have nothing against that weird tradition of the Italians' to color characters' shoes yellow, I think coloring Young Goofy's (anarchic, by the way) snickers in that colour is going a bit too far.