(WJW) – British actor Ian Gelder, known for portraying Kevan Lannister in the hit HBO series “Game of Thrones,” has passed away.

Gelder’s husband, Ben Daniels, confirmed the news on Instagram on Tuesday, saying Gelder died Monday while battling bile duct cancer.

According to the Cleveland Clinic, bile duct cancer, or Cholangiocarcinoma, “is a rare, aggressive form of cancer. It often affects adults in their 70s and has spread beyond the bile ducts by the time healthcare providers diagnose it.”

He passed away just five months after being diagnosed with cancer in December, his husband said, sharing a smiling photo of the couple together.

“He was my absolute rock and we’d been partners for more than 30 years,” the post said, in part. “If we weren’t together we spoke to each other everyday.”

Gelder was 74 years old.

Daniels went on to say that Gelder was “the kindest, most generous spirited and loving human being.”

“He was a wonderful wonderful actor and everyone who worked with him was touched by his heart and light,” the post said. “I honestly don’t know what I’ll do without him by my side.”

The photo was taken around Christmas time, after Gelder had been released from the hospital, Daniels said.

“He coped with his dreadful illness with such bravery, with no self pity. Ever. He was remarkable and will be so missed.”

Gelder is best known for roles in “Game of Thrones” and “Torchwood,” according to his IMDB page.