Lakes Kivu and Malawi are related in that they are both rift valley lakes. A rift valley is a lowland region that is formed by the sinking and spreading apart of the Earth's crust, and it often creates a depression that can fill with water to form a lake. Both Lake Kivu and Lake Malawi are located in the East African Rift, which is a geological formation that stretches across several countries in East Africa.
While both lakes may attract tourists for their natural beauty and recreational opportunities, it is their shared characteristic as rift valley lakes that is the primary way in which they are related.