Once George started writing songs, his and Paul’s relationship started cracking.
Paul, John Lennon, and The Beatles’ producer, George Martin, acted condescendingly when he came forward with his tunes. George felt like a junior member, and Paul started treating him like a glorified session man. Paul told George to play what he wanted, and George was rarely able to give his input. Meanwhile, George had to help Paul do tons of his songs before Paul even considered recording one of George’s.
Source: cheatsheet.com