Charles:
Your related to Logan, your his younger sister.
Erik:
Your related to Gamora, your her twin sister, your not identical though.
Hank:
Your related to Tony Stark, your his little sister.
Alex:
Your related to Barry Allen, your 1 year older than him.
Scott:
Your related to Starlord, your his younger sisters.
Kurt:
Your related to Scott Lang, your his niece.
Peter/Peitro:
Your related to Steve Rodgers, your his daughter.
Logan:
Your related to Jean, your her cousin.