Mary Cheney, the openly gay daughter of former vice president Dick Cheney and younger sister of Wyoming U.S. Senate candidate Liz Cheney (R), said Sunday that her sister is on the "wrong side of history" by opposing same-sex marriage.
Earlier Sunday, Liz Cheney appeared on "Fox News Sunday" and was asked to clarify her position on gay marriage.
"I don't believe we ought to discriminate against people because of their sexual orientation. If people are in a same-sex relationship and they want their partner to be able to have health benefits or be designated as a beneficiary in your life insurance, there's no reason we shouldn't do that," Cheney said.
She continued, "I also don't support amending the Constitution on this issue.. I do believe it's an issue that's got to be left up to states. I do believe in the traditional definition of marriage."
Mary Cheney's wife, Heather Poe, responded to her sister-in-law's remarks in a Facebook post.
"Liz has been a guest in our home, has spent time and shared holidays with our children, and when Mary and I got married in 2012 - she didn't hesitate to tell us how happy she was for us. To have her now say she doesn't support our right to marry is offensive to say the least," Poe wrote. "I can't help but wonder how Liz would feel if as she moved from state to state, she discovered that her family was protected in one but not the other."
Mary Cheney then shared Poe's remarks on her own Facebook page.
"Couldn't have said it better myself," she wrote. "Liz - this isn't just an issue on which we disagree - you're just wrong - and on the wrong side of history."
Mary Cheney has publicly rebuked her sister's gay marriage stance in the past.
"For the record, I love my sister, but she is dead wrong on the issue of marriage," she wrote on Facebook earlier this year. "Freedom means freedom for everyone.. That means that all families — regardless of how they look or how they are made — all families are entitled to the same rights, privileges and protections as every other."
Former vice president Cheney endorsed same-sex marriage in 2009.