Snoopy's siblings

From Peanuts Wiki

Spike - First appeared August 13, 1975. Lives in a desert outside needles, California.

Belle - First appeared June 28, 1976. Snoopy's only sister. She has an unnamed teenage son.

Marbles - First appeared September 28, 1982. The smart one in the family.

Olaf - First appeared January 24, 1989. The family misfit. "Ugly Olaf".

Andy - First appeared February 14, 1994. Shaggy dog. Tag-teams with Olaf.

The whole family seems to be in on Snoopy's WWI Flying ace thing. Spike is often shown in the trenches as an infantry grunt and Belle appears as a Red Cross nurse for both brothers. Even Snoopy's mother is shown as a nurse on occasion.

On one occasion Snoopy's Father is shown receiving a Father's Day Card. He comments that "all eight of them signed it".We only know of six children (Snoopy, Spike, Belle, Marbles, Olaf and Andy). Who are Snoopy's two unnamed siblings?

Info from the book 50 Years of Happiness by Derrick Bang