Cassius's Links
Cain is the object of Cas's affection. Cas isn't IN love with Cain. But he is the only Griffolk Cas cares to associate with and be genuine around. Cain is the only griffolk Cas would ever entertain being in a romantic relationship with (note: it will never happen, both because Cain isn't interested, and Cas being aromantic).
Rather rocky friendship. Cain tolerates Cas.