Dudley Dursley's children

The children of Dudley Dursley and Mrs. Dursley would occasionally be visited by their magical cousins, the two sons and daughter of their father's cousin Harry Potter. While they played with James, Albus, and Lily, the children's fathers would sit silently together.

Magical Abilities
Rowling has once said in an interview that she though of having Dudley´s children as wizards and witches but later changed her mind saying that the magical abilities would never work with Vernon Dursley´s DNA.