Carly Simon is in mourning after both of her sisters — the Broadway composer, Lucy Simon, and former opera singer, Joanna Simon — died this week just one day apart of each other.

According to multiple reports, the “You’re So Vain” singer’s two sisters — whose father, Richard Simon, was the publishing magnate and co-founder of publishing giant Simon & Schuster — died from cancer. Joanna died Wednesday from thyroid cancer and Lucy on Thursday following a long battle with breast cancer. Joanna was 85 and Lucy 82, respectively. It’s been reported that Joanna died in a Manhattan hospital while Lucy died at her home in Piedmont, New York.

Lucy and Carly got their start in music as the folk singing duo The Simon Sisters. They would go on to release the song “Wynken, Blynken & Nod,” which charted at No. 73 on the Billboard Hot 100 in 1964. Carly’s career would eventually take off, and she...