Is Andre the giant the big show's uncle in real life?

No, Big Show was billed to be Andre's son which means it was not real (kayfabe). The reason why they start saying he was Andre's son was because Big Show is the next wrestler similar to Andre they both had a growth disease which is a disease where your body won't stop growing and you need surgery to fix it. Big Show had the surgery in the early 90s but I don't think Andre got it.

Answer

No... it was made up as a publicity stunt to get the audiences attention