ふしぎなメルモ (1971)

This series centered on Melmo, a nine-year-old girl whose mother is killed in an auto accident and has to then take care of her two younger brothers (Totoo and Touch). While in Heaven, the children's mother is given one wish. Her wish is that Melmo (the oldest out of her 3 children ) will be allowed to grow up more quickly than usual, since their lives as children will be difficult without their parents.