CHEYENNE, Wyo. (AP) — The parents of Liz Cheney and Mary Cheney are speaking up as their daughters engage in a testy public debate over gay marriage.

Liz Cheney is running in a Republican primary for a U.S. Senate seat from Wyoming. She told "Fox News Sunday" she disagrees with her sister Mary Cheney, who is married to a woman, over the topic of same-sex marriage.

Mary Cheney responded on Facebook: "You're just wrong."

Former Vice President Dick Cheney and his wife, Lynne Cheney, said in a statement Monday that their family has dealt with this issue privately for many years.

They said they are "pained to see it become public."

Liz Cheney says she believes in a "traditional definition" of marriage and states should be allowed to decide the matter for themselves.