Thanks.

It says "You, the Primary Insured Person, and your Immediate Family
Members are automatically covered. Immediate Family Member
means your Spouse or Domestic Partner and their children, including
adopted children or step-children; legal guardians or wards; siblings
or siblings-in-law; parents or parents-in-law; grandparents or
grandchildren; aunts or uncles; nieces or nephews. "

That doesn't tell me whether I have to be on the same flight.