“His whole family is gathered together and we are all totally bereft,” the composer said.
The legendary composer recently revealed that eldest son Nick has been battling gastric cancer.
The actor called out of Broadway's Funny Girl to be by the 2-year-old's bedside.
The cult favorite musical series ran on NBC from 2012 to 2013.
The siblings capped off their five-night residency with an enthralling mix of yet-to-be-released tracks and greatest hits.
“We are all praying that Nick will turn the corner,” the Oscar-winning composer said.
The moment occurred during the band's five-night Broadway residency at the Marquis Theatre.
The Jon M. Chu-directed film adaptation of the popular Broadway musical was originally slated to premiere later next year.
The Apple TV+ series returns to lampoon a new era of musicals later this spring.
The play is currently in previews at The Public Theater in New York City, opening March 15.
