From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
Future Gyumao was one of the few characters to survive the Artificial Human attack. He was seen still living with Future Son Chichi and followed the little news about Future Son Gohan that reached them. Because he was shown to be living with Chichi, it is likely his kingdom had fallen victim to the rampage around Planet Earth by Future Artificial Human No. 17's and Future Artificial Human No. 18's when most civilizations were attacked, though it is unknown how he had survived their attack.