I remember reading in another thread (Is Backtrack is derivative of Ubuntu?) that Kali Linux is based on Debian. Can someone clarify?
Not, it is not. It is based on Debian.
Kali Linux is a Debian-derived Linux distribution designed for digital forensics and penetration testing.
The only thing related with Backtrack is that the authors of Backtrack has participated on this project too.
From the creators of BackTrack comes Kali Linux
It's not clear what you're asking, here.
Ubuntu is based on Debian. Anything based upon Ubuntu is therefore also based on Debian.
Kali is definitely a Debian-based distribution (which is the term used to describe any child/inheritor distribution of Debian, including Ubuntu which is based directly off Debian, and Mint, which is based off Ubuntu and therefore on Debian)
Kali may be based upon Ubuntu.