Without The Everly Brothers, there could not have been a John and Paul (The Beatles), Tom and Jerry, or even a "Sweet Child O' Mine"... They were top-selling country-influenced rock and roll performers, best known for close harmony singing. Their greatest period of chart success came between 1957 and 1961. Hits included such songs as "Bye Bye Love," "All I Have to Do Is Dream" (my mom and dad's "song"), "Bird Dog," "Til I Kissed You," "When Will I Be Loved," and "Cathy's Clown."
Both The Beatles and The Beach Boys developed their early singing style by performing Everlys covers. The Beatles based the vocal arrangement of their song "Please Please Me" upon that of "Cathy's Clown." The duo split in 1973, but reformed in 1983 with a new album produced by Dave Edmunds. "On the Wings of a Nightingale," written by Paul McCartney for the brothers, became a hit single in both the US and UK, and their 1983 Reunion Concert at the Royal Albert Hall in London was well received (source: Wikipedia).
Here they are at that Royal Albert Hall concert performing "Wake Up Little Susie," which was a #1 hit for them back in 1957:
Again from that Royal Albert Hall performance, here they are doing "Walk Right Back," a #1 hit for them in the UK in 1961:
And here's the 1984 music video for that McCartney-penned comeback song (if you are curious, here's McCartney's 1984 demo), "On the Wings of a Nightingale":