Board Thread:Questions and Answers/@comment-241978-20141030044711/@comment-24228112-20141030070534

Basically, I just assume that Verdona and Max had another child that did have the spark and Verdona took said child with her to her planet where they met another Anodite and had Sunny. In the "Gwen 10" episode of the original series, Ben and Gwen mentioned an "Uncle Manny" so it is possible that this uncle could be Sunny's father.

As for why Max didn't mention this other child? When does he spend time with his other children? He's busy preventing the world from ending.