Unrelated is a good way to describe things that aren't connected or linked in any way. You might insist that your dented car bumper is unrelated to your neighbor's smashed mailbox.
Things that have no connection are unrelated: your excellent test grade is unrelated to the shoes your wore on the day you took it, and your inability remember the name of the movie you just watched is unrelated to the fact that the sun is shining. You can also describe two people who aren't in the same family as unrelated. The Latin root is relatus, a past participle of referre, "bring back."