Fadingcall used to be one who was very confrontational, aggressive and often picked fights with Tanagerflight when they were both in their apprenticeship. Their rivalry was a mutual thing, Tanagerflight hated Fadingcall because he was taking the spotlight, and Fadingcall hated Tanagerflight because he would always call him “Leader’s pet” because Riverstar favoured him over the other apprentices and would often pick fights with him. (Their relationship is very much like Lance and Keith from Voltron) (As well as perhaps Bakugo and Deku to some extent). Though over their apprenticeship Fadingcall learned how to work with, or around, Tanagerflight’s need to always challenge him. 
Fadingcall does know about his role as the reincarnation of Fadedstar, though he never knows what to do, and he’s unsure if he’s supposed to be the leader of Fadedclan to appease Fadingstar and often has his doubts if he was the right choice or not. 
Further expanding on his relationship with Tanager, they eventually grew to love each other and are known as Fadedclan’s gay power couple (the straight power couple being Bluestone and Riverstar). They grew to accept each other’s roles in the clan and worked together, Tanager even being the one to comfort Fadingcall when he doesn’t know what to do about being a reincarnation of such an important cat in his clan’s history.