<Li> Toby Stephens as John Robinson, a former U.S. Navy SEAL, and husband to Maureen . He is the biological father of Maureen's two youngest children . </Li> <Li> Maxwell Jenkins as Will Robinson, the 11 - year - old son and youngest child of Maureen and John Robinson . He forms a tight bond with the Robot, whom he saves from destruction during a forest fire . </Li> <Li> Taylor Russell as Judy Robinson, Maureen's 18 - year - old biracial daughter and eldest child . She is a mission doctor, having received accelerated medical training . </Li> <Li> Mina Sundwall as Penny Robinson, the 15 - year - old daughter and middle Robinson child . </Li>

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