Folke had a sister Rut who married Hjalmar Atterbom.
She was very talented and only a very few drawings have survived.
This drawing is of "Tante Axeline", a friend of her father ( Axel Jonsson). It has been difficult to establish exactly who Tante Axeline is but she is often mentioned in grandfather Folke's letters to Olga ("My Darling Olga").
Rut and Folke's mother Ragnhild Jonsson died very young of diabetes. She was also an artist but I have sadly not found any of her work.