How many children did Zeb and Esther Walton have?

In one episode Esther states that she had bore and raised three children in that house, but the only two that are ever mentioned are John and his brother Ben who died in World War I, and who John named one of his children after.

In the episode "The Dust Bowl Cousins" Matt Walton is mentioned as Cora Walton Denby's father, who sold his land back to his father, Zeb. Cora, her husband Ham (Hamilton) and son Job, visit the Walton's while waiting for a job in Newport News, Virgina, after they lose their farm in Kansas due to the drought (Dust Bowl.) It is spoken by Earl Hamner, Jr. in the closing scene that they finally settled in upstate New York.

In season 2, episode 15, it is revealed that Zeb and Esther had three children; John (John-Boy's father), Benjamin (who died in World War I) and one who was never named. I imagine either the writers left it open for further story-line development, or it was forgotten.

Matthew (Matt) Walton is Zeb's brother (and therefore, John's uncle.) Their father's name was Samuel. He had four sons; Henry (oldest), Zebulon, Benjamin, and Matthew. Matt sold his share of the land to his brother, Zeb, and went west. Matt is Cora's father, Cora married Ham Denby, as mentioned above.

More under Esther here:

https://en.m.wikipedia.org/wiki/List_of_The_Waltons_characters