Allison Blixt and Stefania Zaccari are caught in a complicated Catch-22.

In theory, the London-based binational same-sex couple could move to the United States, where Blixt was born and where the couple first met, in order to start the process of securing citizenship for the Italian Zaccari.

But because the U.S. Embassy has already denied citizenship to one of their two sons—2-year-old Lucas, who was carried by Zaccari—they wouldn’t be able to come stateside without splitting up their young family.

“What would we do?” a frustrated Zaccari asked in an interview with The Daily Beast. “We leave Lucas in the U.K. by himself?”

Separating Lucas from his younger brother Massimiliano is, of course, not a real option—and the suggestion that Lucas is somehow less Blixt’s child than the one she carried herself is one the couple finds deeply hurtful.

“To us—to Stefania and I—Lucas and Massi are the same to both of us,” Blixt told The Daily Beast. “And the embassy is saying, ‘No, they’re not the same, Lucas is less of your child than Massi is,’ and that’s offensive.”

Blixt is now a plaintiff in a lawsuit filed against the U.S. State Department earlier this week by the LGBT immigrant rights organization Immigration Equality over the denial of citizenship to Lucas.

Immigration Equality is also simultaneously representing a gay couple in Los Angeles, Andrew and Elad Dvash-Banks, who are facing a similar predicament: As the Associated Press reported, although the gay couple gave birth to twin sons through a donor using sperm from both men, the American consulate in Toronto denied citizenship to one of their boys, Ethan, on the grounds that his biological father is Elad, an Israeli citizen.

“I started crying,” Andrew Dvash-Banks, a U.S. citizen, told the AP, recounting the experience of being told by a consular official that the boys needed to undergo a DNA test. “These are twins, how can you differentiate between them? They were born minutes apart.”

State Department policy regarding the transmission of U.S. citizenship to children born abroad stipulates that “at least one biological parent must have been a U.S. citizen when the child was born”—and a State Department website about the use of assisted reproductive technology and surrogacy abroad states that “if the child does not have a biological connection to a U.S. citizen parent, the child will not be a U.S. citizen at birth.”

Immigration Equality, however, maintains in the official complaint on Blixt’s behalf that the Immigration and Nationality Act allows for citizenship to be given to any children born abroad who have at least one U.S. citizen parent (PDF).

Section 301(g) of the INA states that “citizens of the United States at birth” will include “a person born outside the geographical limits of the United States and its parents one of whom is an alien, and the other a citizen of the United States,” provided the citizen has lived in the U.S. for a certain amount of time. No stipulation is made in this section that the citizen parent must be the biological parent of the newborn child.

“We do not comment on pending litigation,” a U.S. State Department official told The Daily Beast.

Neither of the two couples represented by Immigration Equality lived in the United States at the time they gave birth to their children, but both were already married. And although the Dvash-Banks family has gone ahead and moved to Los Angeles, young Ethan doesn’t have legal status now that his tourist visa has expired, as the AP reported.

Blixt and Zaccari told The Daily Beast that they have no immediate plans to move to the United States—but they at least want to keep the option on the table in the years to come. In fact, if the U.S. had legalized same-sex marriage much sooner, they never would have moved to London in the first place.

Zaccari met Blixt at a bar in Brooklyn on her first night of a 2006 vacation and they “pretty much have been together since,” as Zaccari told The Daily Beast.

But when it became clear that there was no way to get Zaccari to the United States on a more permanent basis—and when Blixt, a lawyer, was granted a transfer to her firm’s London office—the pair reluctantly moved to England together in April 2008.

“I was really, really angry when we first moved here because we didn’t actually want to move here—we wanted to live in New York and had basically been kicked out,” Blixt told The Daily Beast. “I had been kicked out in the sense that I could either choose to be with the person I loved or I could stay in New York without her—and I decided that she was more important.”

Briefly visiting the United States the following month for Blixt’s sister’s wedding only underscored the isolation the couple felt in their new home across the Atlantic.

“I burst into tears [after the wedding] because I just felt like I was leaving everyone that I cared about except for the person that I wanted to be with,” Blixt said.

But the couple proceeded to build a life in London, obtaining a civil partnership that they converted into a marriage in January 2015, when same-sex marriage was legalized in England, as the complaint notes. Zaccari gave birth to Lucas using an unknown donor that same month and in 2017, Blixt, using the same donor, gave birth to Massimiliano.

That means the two children are not just legally and socially but biologically brothers as well—the only difference being that they were carried by different mothers.

“That distinction should make no difference to Lucas’ eligibility for U.S. citizenship as a child demonstrably not born out of wedlock,” the complaint states. “But to the State Department, this is all the difference in the world.”

When the couple tried and failed to obtain citizenship for Lucas, allegedly encountering “invasive questions” about how, exactly, the child had been conceived, Blixt was floored.

“It just flashed me back to all of the feelings that I had felt in 2008 of anger and frustration and hurt and rejection—but now it wasn’t just directed at me, it was directed at my child,” she said, “And that was a lot to bear.”

According to the complaint, the couple tried twice to secure citizenship for Lucas—once in 2015 after he was born, and again in 2017 after Massimiliano was born.

The second time, the State Department issued a letter saying: “It has been determined that there is not a biological relationship between the U.S. citizen mother and child, through either a genetic parental relationship or a gestational relationship, as required under the provisions of section 309(c) of the Immigration and Nationality Act.”

That section, as Immigration Equality notes, is meant to apply to “children born out of wedlock”—even though Blixt and Zaccari have been married since 2015. A similar issue is at stake in the Dvash-Banks case: Their lawsuit alleges that since the State Department did not consider Ethan to be a citizen, requiring the couple to submit DNA tests for their children, that they must perceive the boy as being born “out of wedlock.”

Blixt and Zaccari are hopeful that the legal action can resolve the uneven distribution of citizenship across their family.

“I’m just really hopeful that this can be fixed,” Zaccari told The Daily Beast. “We are optimistic and we have to be positive and we’ll do our best to protect our kids.”

As complicated as their predicament might be, their lawsuit maintains that the matter of their relationship to Lucas is a simple one: “Allison [Blixt] and Stefania [Zaccari] are Lucas’ parents in all relevant respects. They are Lucas’ legal birth parents, and his birth certificate lists only Allison and Stefania as parents. No one else has ever claimed to be or been declared his parent. Allison and Stefania made the decision to bring Lucas into this world and into their family together, and have raised Lucas together since the day he was born.”

Whether that litany of parental proofs is enough for the State Department remains to be seen.