Q: In this task, you're given passages that contain mentions of names of people, places, or things. Some of these mentions refer to the same person, place, or thing. Your job is to write questions that evaluate one's understanding of such references. Good questions are expected to link pronouns (she, her, him, his, their, etc.) or other mentions to people, places, or things to which they may refer. Do not ask questions that can be answered correctly without understanding the paragraph or having multiple answers. Avoid questions that do not link phrases referring to the same entity. For each of your questions, the answer should be one or more phrases in the paragraph, and it should be unambiguous.
Passage: The film is based on actual events, beginning in August 1941.  Nazi Einsatzgruppen (task forces) are sweeping through Eastern Europe, systematically killing Jews. Among the survivors not killed or restricted to ghettoes are the Belarusian Jewish Bielski brothers: Tuvia, Zus, Asael and Aron. Their parents are dead, killed by local police under orders from the occupying Germans. The brothers flee to the Naliboki Forest, vowing to avenge the deaths of their parents.
They encounter other Jewish escapees hiding in the forest, and the brothers take them under their protection and leadership. Tuvia kills the local Auxiliary Police chief responsible for his parents' deaths. Over the next year, they shelter a growing number of refugees, raiding local farms for food and supplies and moving their camp whenever they are discovered by the collaborationist police. Bielski brothers stage raids on the Germans and their collaborators. Casualties cause Tuvia to reconsider this approach because of the risk to the hiding Jews. Rivalry between the two eldest brothers, Tuvia and Zus, fuels a disagreement between them about their future; as winter approaches, Zus decides to leave the camp and join a local company of Soviet partisans, while his older brother Tuvia remains with the camp as their leader. An arrangement is made between the two groups in which the Soviet partisans agree to protect the Jewish camp in exchange for supplies.
A:
Who are the two  youngest of the Bielski brothers?