The Ghoul Kids are bratty kids that lived in a pumpkin Tree House in Ooga Booga. According to Dr. Cadaver they had died 130 years before, and had never grown up since. Their names or nicknames are Nasty and Nsatier.
Behind the scenes
In the credits, they are known as Ghoul Kid 1, and Ghoul Kid 2. The KQ7 Authorized Guide suggests that their names are Nasty and Nsatier (mispelling of 'Nastier'?).