Roald Dahl had 3 "blood related sisters." (I say this because he lived with his 2 other step siblings too.) He was the only boy. His sisters names were: Alfhild, Else, Asta. SORRY, I MADE A MISTAKE. ASTRI, (WHO IS BELIEVED TO BE ROALD DAHL'S SISTER) IS HIS "STEP" SISTER. SHE WAS THE ONE WHO DIED WHEN ROALD DAHL WAS 3 YEARS OLD.