Qrow becoming a father figure to Mercury is such an underrated scenario it hurts me. Besides Qrow's personal villain being Tyrian who is tormenting Mercury as we speak, their individual narratives, albeit on opposite sides of the war, complement each-other so well.
Qrow saw no value in his life because of his semblance bringing harm to those he loved so he isolated himself in addiction and pledged unconditional loyalty to someone who lied and (to an extent) used him. Mercury had his semblance taken away from him for being "weak", which led him to reduce his personal value to strength, latching onto anyone to whom his skillset as an assassin can be useful in exchange for safety.
At least an interaction over their self hatred leading them to unhealthily follow people who gave them value and purpose, even if treated as a means to an end.