Random Riddle: The Opposite Gender

Charlie is the opposite gender.

If Jordan is Sam’s only daughter, then Jordan cannot have a sister. Therefore, Jordan must be Sam’s brother and a male.

If Jordan’s sister is Alex, then fact 1 tells us that Sam is Charlie’s only son. But since Jordan is Sam’s brother, Sam cannot be Charlie’s only son. Therefore, Charlie must be Jordan’s sister.

Since Sam is Jordan and Charlie’s sibling, Alex must be Charlie’s son. Now we know that Alex and Jordan are male, while Charlie is female.