David Monagan, the author of the story, also apologized, calling the mistake the worst he has ever made, the Irish Independent reported. Monagan, a U.S. citizen, works in Cork, Ireland.
"I made a terrible mistake and I apologize to Michael D. Higgins who I have respect for," he said.
Forbes, the U.S. business magazine published in New York, took the article down from its website hours after it was posted.
Monagan, who said in his apology he was under deadline pressure, may have confused Higgins with one of his rivals in the 2011 presidential election. David Norris, a member of the Senate and gay rights activist, is the first open homosexual to win political office in Ireland.
Higgins, a sociologist and poet, has been married to actress Sabina Coyne since 1974. The couple have four children.