Christian conservative celebrity and presidential hopeful Ben Carson on Friday said that it would be unfair to “other groups” if gay and lesbian couples could marry.

Carson, one of the six announced candidates for the Republican presidential nomination, made his remarks during an interview with CNBC's John Harwood.

“If you change the definition of marriage for one group, what do you say to the next group?” Carson said.

“What is the next group?” Harwood asked.

“Do you say, 'Well we changed it for this group, but that's it, we're not changing it for anybody else.' Does that seem fair?”

“But what other groups are there? … Honest to God, I don't know what you're talking about.”

“Other variations on traditional marriage,” Carson answered.

“You mean like bigamy or something?”

“That's a possibility,” Carson replied.

In 2013, Carson was forced to apologize for comments he made on Fox News suggesting that allowing gay couples to marry would lead to bestiality and pedophilia.

“It's a well-established, fundamental pillar of society, and no group, be the gays, be they NAMBLA, be they people who believe in bestiality – it doesn't matter what they are – they don't get to change the definition,” he said, referring to the North American Man Boy Love Association, a group which is thought to no longer exist.

After a more recent uproar, Carson pledged to no longer talk about gay rights, a promise he's finding difficult to keep.