Just like with his sister, magic was needed when Sam was conceived. A very difficult pregnancy and a even more complicated birth almost put an end on the dream of a bigger family, but every Stark was a fighter and Sam wasn't different. His family suspects that the strength he showed in his recovery as a baby is superhuman and inherited from his father, but other than that, they have no evidence of any supernatural power the boy might have.

Abby’s birth was something miraculous in itself: being the child of two creatures considered unable to conceive (a shapeshifter that turns on a giant poisonous sea serpent and a mermaid), it’s not a surprise that a little bit of magic was involved in her creation. It’s also not a surprise that her favorite place to be is the ocean. To the present day, Abby, already in her teens, didn’t show any supernatural abilities, so it remains a mystery if she actually has some.