Feuding Sisters are normally found around safer areas, playgrounds, and other recreational areas. They will challenge you to a Double Battle upon sight. What makes this class of trainers unique is their tendency to attack one another. Feuding Sisters are more likely to use moves such as Earthquake which affect every Pokémon in battle, or just using a move on their sister. However, the majority of the battle plays out normally.
The older sister uses a wide variety of Pokémon - often with a type advantage over her younger sister - and the younger sister tends to use smaller Pokémon, or ones which are useful against her sister's team.
Ground
Ground/Fighting
Ghost
Normal/Rock
Normal