(CNN) — Despite long-term relationships, shared children and steadfastness to each other in sickness and in health, for richer and for poorer, same-sex couples like Heather McIver and Suzanne Lowe, Kelli Evans and Karen Wade, and J. Wesley Thompson and Trey Owen know that their commitments could be invalidated with enough ballots. They live in North Carolina, which will be conducting a referendum on gay marriage next month.

On May 8, voters in North Carolina will head to the polls to vote on Amendment 1, a proposed amendment to the state constitution that would define “marriage between one man and one woman” as “the only domestic legal union that shall be valid or recognized.” According to same-sex marriage advocacy group Marriage Equality, North Carolina is one of 20 states that are considering whether to allow or ban same-sex relationships. Twenty-one states recognize some form of same-sex relationships, either as marriage, civil union or domestic partnership. Thirty states ban same-sex marriage by law, constitutional amendment or both.

Each of the above couples participated in Commitment NC , a documentary photo project that aims to show the faces of the families that would be affected by passage of Amendment 1. It’s the brainchild of Justin Cook, an independent photographer based in Durham, North Carolina, who says he wanted to show the “real love and real lives” of gay and lesbian couples. Commitment NC has also grown to include images and stories from a similar project, Love for All, by another group of photographers capturing the lives of unmarried couples, gay and straight.

Same-sex marriage in North Carolina is already banned under existing legislation, but supporters of the amendment say it’s needed to protect the ban from “activist judges” who might overturn it. Conservative Christian groups are among the amendment’s most fervent supporters.

Opponents of the amendment say that it would enshrine discrimination against gays and lesbians into the constitution, and would also hurt male-female couples who are committed, but have chosen not to marry. Among those opposed to Amendment 1 are members of the business community, who say that it could keep companies and talent from settling in the state.

Legal experts say that the amendment would also impact the prosecution of domestic violence charges between unmarried partners, and the child custody rights of non-biological parents of any sexual orientation in the event of divorce or death of one partner.

So far, Cook has photographed 20 same-sex couples in long-term committed relationships, and plans to do several more.

Heather McIver and her partner Suzanne Lowe were photographed in front of their church, a white clapboard building in rural North Carolina that is home to the Spring Friends Meeting, a Quaker fellowship. McIver and Lowe have been together since 1993, and they are raising two daughters, 7-year-old Annika and 3-year-old Celie.

For McIver, commitment means “that we have a direction we’re moving in that we still agree on. We share our values enough that we strive to fulfill those values.” Those values are shared by the other members of their meeting, who, unbidden, voted to pass a resolution opposing Amendment 1.

McIver said her biggest worries are about how passage of the Amendment would affect her family at its most vulnerable points. They’re scenarios prefaced with the words “God forbid” — one partner’s lack of legal ability to make decisions on behalf of the other in the event of death or incapacitation, the loss of the health insurance coverage she has through her domestic partnership with Lowe, a challenge mounted to Lowe’s custody rights because she is a parent of Annika and Celie by adoption and not by biology, like McIver.

Kelli Evans and her partner of 17 years, Karen Wade, have similar concerns about Amendment 1’s potential impact on their family — which includes 3-year-old triplets.

“It could destroy our family unit. That was one of the major reasons we wanted to be a part of (Commitment NC),” Evans said. “I think it’s very important to educate people and get them away from the gay marriage issue. If they could see that it’s a family they’re affecting, maybe they could sit down and think about the issue before they vote on Election Day.”

Evans maintains that the main difference between her family and any other is that hers includes very active triplets — not that she is in a same-sex relationship.

“It’s two loving adults that have been together for so long,” Evans said. “We decided we wanted to expand the love and bring children into the picture. One of us gets up and goes to work, the other stays with the kids. We bicker about ridiculous things. We’re a family. I’m not knocking on your door trying to destroy your family, so why are you trying to destroy mine?”

J. Wesley Thompson and Trey Owen have weathered intense storms throughout their 25-year relationship, including Owen’s battle with an aggressive and usually fatal form of leukemia. They were married in Canada in 2006, 20 years to the day and hour that they met.

Thompson and Owen say that participating in the project has given them a chance to be positive role models for gay and lesbian young people, showing what a loving, committed relationship can look like.

Owen said it especially bothers him that the pro-Amendment 1 effort is being backed by so many fellow Christians. Owen grew up in a conservative Christian church, and he and Thompson now belong to an Episcopalian church.

“Most gay people I know turn to religion for help, and most of what they find is hate and rejection,” Owen said. “Jesus mentioned divorce many times, and never said anything about same sex couples. If the greatest commandment is to love, the church has fallen so short. That’s my biggest challenge, accepting that in my heart without me becoming even more angry than I already am about it. The greatest benefit is the hope that we might be doing something that helps change things a little bit for the better.”