“The train has left the station,” said Avi Rubel, a founder of Honeymoon Israel, which expects to send 360 couples this year. Mr. Rubel said the program has no political or religious agenda.
“We don’t care what you believe in,” he said. “You married into our family, so you’re in our family. We want couples to explore the issues on their own terms. We’re not trying to dictate how anybody feels about being Jewish or about Israel.”
Ms. Mask and Mr. Diamond went to Israel in February, three months after their wedding, with the first group organized out of New York City. Ms. Mask was especially relieved to meet so many other Christians in her situation. “It helped address this fear that I will lose part of my identity,” she said.
For Mr. Diamond, the trip “was all about an open-mindedness to the idea that there are many kinds of Jewish families,” he said. “That’s not something I’ve been exposed to most of my life: a celebration instead of a grudging acceptance.”
Seth Preminger, 31, and Tracy Lyons, 30, each assumed they would marry within their own faiths. Dr. Preminger, a child and adolescent psychologist in Chicago who was raised Jewish, and Dr. Lyons, a pediatrician in Chicago who was raised Catholic, met in July 2011. “As a little girl, the only thing I’d ever planned for my wedding was what church I’d get married in and what church music I’d have,” Dr. Lyons said.
Neither realized how stressful planning an interfaith wedding would be. The Catholic clergyman who agreed to be an officiant wanted to marry them in a church, but that made Dr. Preminger uncomfortable. It was difficult to find a rabbi willing to be part of a joint ceremony.
After much searching with Google, they found the Interfaith Family School in Chicago, run by Catholics and Jews. The school, which offers a kindergarten-through-eighth-grade curriculum for children whose families consider themselves “both,” and which also has a couple’s counseling group, invited Dr. Lyons and Dr. Preminger to attend a student presentation.
“It was really exciting for us to hear these kids talk about growing up in an environment that supports both faiths, especially as we were planning our wedding,” Dr. Lyons said. “They help you explain the different traditions to extended family.”
Dr. Preminger said their wedding in May 2015 at the Kenmare Loft, a former factory in Chicago, raised a few eyebrows, but everyone eventually came around.
Another organization, InterfaithFamily, which is overseen by rabbis, demonstrates the ripple effect of this new attitude. The nonprofit started as a website, interfaithfamily.com, to help couples plan interfaith weddings and find rabbis willing to jointly officiate ceremonies. Within the last five years, the organization has opened offices in eight cities where the group hosts couples discussion groups, religious services and social events.
“Couples need safe spaces to be with others just like them,” said Rabbi Ari Moffic, who heads the Chicago branch. “If you Google ‘interfaith marriage,’ you’ll still find negative headlines.”
“The American Jewish community sees this as a public concern for Jews at large,” said Helen Kim, an associate professor of sociology at Whitman College in Walla Walla, Wash. “They want to mobilize the larger community.”
Dr. Kim is a second-generation Korean-American who was raised without religion and adopted Judaism after marrying Noah Leavitt, an associate dean at Whitman. The couple recently wrote a book, “JewAsian: Race, Religion, and Identity for America’s Newest Jews.” There are no hard statistics, but Dr. Kim, who said she has noticed a rise in Jewish-Asian marriages, has also found that Asians in the United States, who are mostly Christian, aren’t concerned about “dilution of the population” the way Jews are.
On balance, there are fewer resources for couples seeking a more equitable arrangement. Many organizations “say they’re friends of interfaith, but they have a tiny asterisk that says, ‘We want you to have a Jewish home,’” said Eileen O’Farrell Smith, the founder and director of the Interfaith Union, which holds workshops for Christian-Jewish and Christian-Muslim couples in Chicago.
In New York, Interfaith Community runs couples workshops, private counseling sessions and an elementary school curriculum that teaches the fundamentals of Judaism and Christianity for interfaith families.
“In this multicultural, global, diverse world, where people are bringing many differences into a family, the old post-World War II paradigm, where you married the boy next door and everyone went to the same church, has completely changed,” said Sheila Gordon, the group’s president.
Some 100 children are enrolled in Interfaith’s educational programs, Dr. Gordon said, but the number of couples in the premarital workshops has declined, even as the percentage of interfaith marriages has increased.
At least for younger couples, “the millennial ethos of fairness and respect means they don’t feel threatened by entering into this kind of partnership,” she said. In other words, these couples do not think workshops are necessary.
And yet, such programs can be vital for some couples, who do face challenges in joining different faiths.
“It helps to know other people in the same boat,” said Kamran Khan, a Muslim who joined Ms. O’Farrell Smith’s group with his Christian fiancée, Corinne Atty. Their wedding, planned for September in Chicago, has caused a rift, with Mr. Khan’s parents disapproving of his relationship and refusing to talk about it or to attend the wedding. But Mr. Khan wants to discuss the difficult questions with Ms. Atty now, “instead of seven years from now,” he said.
Being a part of the Christian-Muslim group at Interfaith Union, he added, has given him a sense of pride about creating a different kind of family. “We can blaze a trail for others,” Mr. Khan said. “We’re at the forefront of something.”