Corbett was on WHP-TV in Harrisburg when an anchor asked about a statement his lawyers made in a recent court filing, comparing the marriage of gay couples to the marriage of children because neither can legally wed in the state.
"It was an inappropriate analogy, you know," Corbett said. "I think a much better analogy would have been brother and sister, don't you?"
Pennsylvania is the only state in the Northeast that allows neither gay marriage nor civil unions. Its ban on same-sex marriage is being challenged in federal and state courts.
Mark Aronchick, a lawyer for the plaintiffs in that case, called Corbett's remarks "insensitive, insulting and plainly wrong."
"In other words, some kind of incestuous relationship," Aronchick said. "He's just out of touch on this one. Gay people marry for the same reasons straight people do - to express their love and to declare their commitment before friends and family."
Later Friday, Corbett issued a statement saying his "words were not intended to offend anyone" and apologizing if they did. His office said the interview was taped Monday.
"I explained that current Pennsylvania statute delineates categories of individuals unable to obtain a marriage license," he said. "As an example, I cited siblings as one such category, which is clearly defined in state law. My intent was to provide an example of these categories."
He said the legal status of same-sex marriage will be decided with "respect and compassion shown to all sides."
Ted Martin of Equality Pennsylvania, which advocates on behalf of lesbian, gay, bisexual and transgender people, called the governor's remarks "shocking and hurtful."
Corbett, a former federal prosecutor and two-term state attorney general, also said he does not think such a challenge to the state's ban on same-sex marriage belongs in federal court.
"The Supreme Court left it up to the states to determine under their laws as to what is and isn't a marriage," Corbett said. "The federal court shouldn't even be involved in this. But if they say they are, then they're going to make a determination whether the state has the right to determine that a marriage is only between a man and a woman and not between two individuals of the same sex."
Corbett's attorneys included a reference to children in a legal brief in August involving same-sex couples seeking marriage licenses. In the court filing opposing allowing same-sex couples to intervene in the state's lawsuit to bar a suburban Philadelphia county from issuing marriage licenses to same-sex couples, the lawyers made an analogy to a pair of 12-year-olds, saying if the children were issued a marriage license and tried to defend it in court, they wouldn't be taken seriously because the license was never valid.
Corbett later rejected that analogy, saying the case revolved around the question of whether a public official had "the authority to disregard state law based on his own personal legal opinion about the constitutionality of a statute."
A state judge sided with Corbett in that case, ordering the clerk to stop issuing the licenses.
A hearing on the federal challenge to the same-sex marriage ban is scheduled for Wednesday in Harrisburg.