The couple have been together since 1993 and entered into a British civil partnership on the day it came into law in 2005. Their decision to take the next step comes just a few weeks after legislation passed in England to allow same-sex marriage.
"We don't feel the need to take an extra step legally. But since we're committed for life, we feel it's really important to take that step, and take advantage of that amazing change in legislation," Furnish said. "We all live by example."
The couple have two children together: Zachary, 3, and Elijah, 16 months.
Unlike their lavish 2005 reception, Furnish said they plan to keep things simple when they wed. "I think what we'll do is go to a registry office in England in May, and take the boys with us, and a couple of witnesses," he said.