Transcript for Pope Francis becomes first pope to endorse civil unions for gay couples
news from the Vatican tonight. Pope Francis voicing support for same sex civil unions. The first pope in history to do so. The pope saying homosexual people have the right to be in a family, that they are children of god. Here's our foreign correspondent James Longman tonight. Reporter: Tonight, an historic shift from the leader of an ancient institution. Pope Francis becoming the first pope in the catholic church's 2,000 year history, to endorse civil unions for gay couples. In the new documentary "Francesco," the pope says, "Homosexual people have a right to be in a family. They are children of god and have a right to a family." It's a major departure from the position of the Vatican's own doctrinal office. The pope adding, "What we have to create is a civil union law. That way they are legally covered. I stood up for that." The pontiff has called for civil unions in the past, but before he became pope. The emphasis on the legitimacy of the lgbt family also notable. Experts calling it a monumental moment. It's a real way of not only speaking pastorally to this group of people but also speaking lovingly and making them feel more welcome in the church. Reporter: Conservative catholics tonight calling for clarity. Thomas Tobin, bishop of Providence, Rhode Island, saying, "The church cannot support the acceptance of objectively immoral relationships." But Francis' words have struck a chord with a younger generation. I never thought that I would see something like that in my lifetime. Reporter: 29-year-old Nicholas Traxler from Minnesota says the pope's comments speak to his heart. It's a difficult road for most lgbtq catholics. I value my faith and my sexuality as equal parts of my identity. It hasn't always been that way. Reporter: Pope Francis has cast himself as the modernizing pope, but he's faced huge opposition from within his on clergy. This latest move could mean the biggest backlash yet, but he may feel he has no choice if he's to survive in a modern age. David?
This transcript has been automatically generated and may not be 100% accurate.