Hypnos's Links
Hypnos is Thanatos younger brother he knows that Thanatos hates him and don't wanna do anything with Hypnos but he don't really care and still follows him. They often fight but usually Hypnos is smart enough to avoid his attacks.
Since Thanatos don't like anyone around him he tries to avoid having Hypnos near him but somehow he always find Thanatos no matter where he is.