How are Rundi and Rwanda’s Kinyarwanda language related?

Rundi (also known as Kirundi) and Kinyarwanda (also known as Rwanda) are closely related Interlacustrine Bantu languages. Both languages are mutually intelligible, meaning that speakers of one can generally understand the other.12

They are classified within the Bantu language family, a large group of languages spoken across much of Africa. Because of their shared linguistic roots and structural similarities, they are considered distinct but highly compatible forms of communication.3412