Just before the encore of their acclaimed show Sibling Revelry, the Callaway sisters stepped into the audience to ask if everyone felt the spirit of music that evening. The Callaways, who were in on the surprise, approached several audience members before asking Robeano how he felt that night.

"I think music makes us all better, and over the years you ladies have made us all better," Robeano said. "And, really, this guy has made me better for so long..." he continued before proposing to his partner, Sean Thomas-Breitfeld, in front of a packed house at 54 Below.

"Sean, there's no pressure," quipped Liz Callaway before Thomas-Breitfeld replied with a "Yes." The audience erupted into cheers and applause as the staff of 54 Below brought out champagne and a cake for the happy couple.

The Callaways then launched into their encore, "Brotherhood of Man," which they adjusted for the romantic evening:

"Oh, that noble feeling
Feels like 'wedding' bells are pealing..."

"[It was] an amazing night," Robeano told Playbill.com. "Liz and Ann worked very hard to make the proposal amazing and special, yet still keep the integrity of their show. They found the perfect balance to make a joyous and memorable moment. The staff at 54 below was unbelievable."

Robeano and Thomas-Breitfeld plan to marry in summer 2015 in New York City.