And next tonight we take you inside a private family feud playing out on the national stage, the two daughters of former vice-president dick cheney, both of them moms, both of them married. One is... See More
And next tonight we take you inside a private family feud playing out on the national stage, the two daughters of former vice-president dick cheney, both of them moms, both of them married. One is straight and the other is gay and now the sisters are squaring off on the meaning of faith and marriage and their parents are weighing in. Jonathan karl. Reporter: It all started when liz cheney, the daughter of the former vice-president came out against same sex marriage in her campaign for senate in wyoming. That's not a surprising position for a republican in wyoming. This is younger sister mary who is married to heather poe and they have two children. I love mary very much and her family very much. This is an issue on which we disagree. Reporter: This isn't just an issue on which we disagree responded mary poe, heather's wife. You're just wrong. Liz has been a guest in her 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 say now she doesn't support our right to marry is offensive to say the at least. Liz shared her post and said i couldn't have said it better. It's not just we respectfully disagree. It's personal. It's angry. Reporter: Public attitude on this have shifted dramatically over the last decade. A strong majority now believe gay marriage should be legal. Just this fall former president george h.W. Bush was a witness at a wedding of two women. We talked to vice-president cheney shortly after they were married last year. Lynn and I were proud and congratulated them. They have provided us with two of our grandkids. Reporter: In a statement the former vice-president and his wife said this is an issue we have dealt with privately for many years and we are pained to see it become public. Jonathan karl, abc news, washington.
This transcript has been automatically generated and may not be 100% accurate.