Simplify the following text for a Grade 7 native English-speaking person.
Original: After Hargreaves 's death in 1988 , his son Adam Hargreaves began writing and illustrating new stories , including four characters that R. Hargreaves had developed before his death .
Simplified: After Hargreaves died in 1988 , his son , Adam Hargreaves , began writing and illustrating new stories about the Mr. Men and Little Miss characters . He created ten new characters ; four of them were inspired by work Roger Hargreaves had produced before his death .