How are the Bengali and Assamese writing systems related?

The Bengali and Assamese writing systems are closely related, as they both descended from the Brahmi script via the eastern variety of the North Indian subdivision. Specifically, both scripts evolved from the proto-Bengali script that emerged in eastern India during the 11th century.12

Because of this shared lineage, the characters used in the Bengali and Assamese scripts generally coincide. While the Bengali script followed a developmental path distinct from that of Devanagari and Oriya, it remains fundamentally linked to the Assamese system through their common ancestral roots in the eastern branch of ancient Indian scripts.21