Totally unrelated? Got a citation for that?
Every living organism uses the “Universal Code” or a slight variation of it, that ‘translates’ DNA “genes” into the Amino Acid sequence of a functioning protein molecular machine.
Moreover every living species has similar variations of the same ubiquitous “housekeeping” genes that perform essential cellular functions.
Archebacteria is a good example of an unrelated class of life.
It has a sulfur electron transport system, instead of oxygen, and is therefore unrelated to all life with an oxygen based electron transport system.
This bacteria lives at deep ocean volcanic vents. I studied it for a bit.