Eli Manning has had to deal with being Archie Manning's son and Peyton Manning's younger brother for most of his public football career. (One assumes he was also Cooper Manning's kid brother for a while, too.) When he committed to Ole Miss way back when, it was implied both that he was following in his father's footsteps and Peyton's, because he was committing to play for the same coach, David Cutcliffe, that turned Peyton into a Heisman Trophy candidate at Tennessee.
And because Eli is younger and had a lesser collegiate career than Peyton's, and entered the NFL with some hullabaloo over his family balking at him playing for the San Diego Chargers, and spent his rookie year sitting with the New York Giants while Peyton won his second consecutive NFL MVP, he's always been seen as the lesser quarterback.