How many people are in the Ewell family in To Kill a Mockingbird? I know there is Bob and Mayella, but how many younger siblings are there?

According to Scout's school gossip (in Chapter 17),
"nobody was quite sure how many children were on the (Ewell) property." Some thought
there were six, and others said nine. Scout only knew that there were dirty Ewell faces
pressed against the windows of the house when people passed by. However, Mayella Ewell
knew how many brothers and sisters she had, and she revealed the answer while she was on
the witness stand (in Chapter 18). When Atticus asked Mayella how many brothers and
sisters she had, Mayella
answered,

"Seb'm."

Assuming
that Mayella meant "seven," that would total eight Ewell children, counting Mayella.
(Mayella, 19, was the oldest, and the only other child mentioned was Burris, Scout's
lice-ridden classmate.) Tom Robinson confirmed this number when he took the stand (in
Chapter 19). He claimed that Mayella told him that
it

" 'took me a slap year to save me seb'm
nickels, but I done it.' "