Sure.
The Redskins had Sonny Jurgenson, nearing the end; and the other guy Billy Kilmer who could barely compete a pass, who started and won Superbowls.
Have you forgotten Jack Kemp when he was nearing the end in the mid 60s, after winning a couple of AFC crowns, and Daryl Lamonica, "the Mad Bomber"? Eventually Lamonica went to the Raiders.
The Giants of the late 50 and early 60s and Charlie Connerly and YA Tittle as one was slowly phased out.
I have purposely looked for examples of an elderly Star, and a rising youngster rather than merely two QBs both vying for the team leadership, like Bledsoe and Brady, Montana and Young etc.