Why does Jeannette think that Erma dislikes her and the other children?

Erma is a cranky old lady. Erma refuses to be called ‘Grandma’ because it makes her feel old. Erma has a grumpy disposition and asks her grandchildren to refrain from laughing in her home. Jeannette sees no resemblance between her grandparents and her father. We wonder if they are actually Rex's parents.