Credit: Andrew H. Walker/Getty Images for LEVIEV

Rich Cronin of 90s boy band LFO died on Wednesday at age 36, CNN confirms. He passed away in a Massachusetts hospital, according to bandmate Brad Fischetti.

Cronin, who wrote and sang the number one smash "Summer Girls," was diagnosed with leukemia in 2005; despite chemotherapy, the disease returned in 2007 and 2008.

The singer-songwriter then underwent a stem cell transplant -- which, according to Fischetti, led to a stroke and severe leg pain.

Even with his medical battles, Cronin reunited with LFO pals Fischetti and Devin Lima for a summer 2009 tour.

His bandmates gave him a large back bedroom on the bus so he could rest in between gigs.

"We had the best time ever," Fischetti said. "He never thought he'd be on stage again."

Fellow boy band star Lance Bass of N Sync paid tribute to Cronin on Twitter late Wednesday. "Sad sad day that Rich Cronin died- was a amazing guy :(" Bass wrote.