Vladmimir and Joe were two male astronauts, Russian and American respectively, who survived the plague due to being on board the International Space Station at the time. During their months trapped on the station, they both became the lovers of crew mate Ciba Weber. When the Soyuz re-entry vessel started to burn on landing, they insisted on pushing her to safety (even though their lives were more valuable for the survival of the human race) as she had become pregnant. Both men died in the subsequent explosion.
When Ciba's baby is born, he is revealed to be Vladimir's son, to whom Natalya Zamyatin often refers to as "The Son of Russia."