Aiden and Ethan Dvash-Banks share pretty much everything. The 16-month-old twins were born four minutes apart, from the same womb, to the same fathers and now they share the same toys in the living room of their Southern California home.

But there is one thing they don't share — Aiden was granted U.S. citizenship and Ethan is living in California on an expired tourist visa.

Why? The State Department says only one is the child of an American. One of the kids has the genetic material of his U.S. citizen father; the other, the genetic material from his other father, an Israeli citizen with a green card. Both boys were born in Canada.

The couple is now suing the State Department with the help of Immigration Equality, an LGBTQ-immigrant-rights organization. It's one of two lawsuits filed this week by married, same-sex couples who had children abroad. In each case one of the children was refused citizenship because he was genetically related to only the foreign parent.

Immigration Equality says it goes against the Immigration and Nationality Act that says children born abroad to at least one U.S. parent get citizenship. But the State Department's interpretation says the child must be biologically related to the U.S. citizen to get the passport.

Andrew Dvash-Banks had made his life with his Israeli husband, Elad, in Canada because before 2013 same-sex marriages weren't legal in the United States and Andrew couldn't sponsor his husband.

Andrew describes applying for his newborns' passports at the U.S. Consulate in Toronto. The Dvash-Bankses had their marriage license and the kids' birth certificates. Everything was in order. They heard their number called; they walked up to the window and greeted the consular officer, who looked a little surprised, they said.

"She started off with, 'Obviously the two of you had to use assisted reproduction in order to have your family,' " Andrew said. " 'Tell me more about that. Tell me about who is genetically related to who.' "

The questions were invasive, probing, embarrassing, he said. He cried; Elad got quiet.

They didn't expect this. As the children of an American citizen, the twins should both inherit citizenship. But the couple used a surrogate abroad. Each child has genes from one of his fathers. And while Andrew and Elad never planned to tell anyone which child had Andrew's DNA and which child had Elad's, the State Department asked for DNA tests.

Two months later, Andrew says, letters came.

"One addressed to Aiden, with a U.S. passport saying congratulations, here is your U.S. passport," he said. "And one addressed to my son Ethan saying we regret to inform you that your application for citizenship has been rejected."

Despite both men being listed on the boys' birth certificates, Elad says, the government made a distinction.

"It was literally black and white, on paper, your kids are different," he said. "That was something that any parent would have a hard time seeing, that the government is discriminating against their kids and treating them differently. It's terrible."

The State Department wouldn't comment for this story because of the pending litigation. But in the department's Foreign Affairs Manual, consular officers are instructed to ask for evidence if they suspect a child doesn't have a biological relationship with the U.S. citizen parent, specifically in cases of surrogacy or "other cases of assisted reproduction."

The discrimination happens in the application, said Aaron Morris, executive director of Immigration Equality. Under the manual's guidance, every single same-sex couple with children would be flagged at a U.S. Embassy.

"Treating same-sex couples differently in this way is illegal and unconstitutional," Morris said. "It is possible that an opposite-sex couple, if they disclose that they had used surrogacy, might have the same problem. But the difference is, in every same-sex couple's case the government is asking deeply invasive questions about the makeup and the creation of the children of same-sex couples. To create a blanket rule in this way that targets only one small population of people and every single member of that class of people is discrimination."

That's how it feels to Allison Blixt and her Italian wife, Stefania Zaccari, parents of two boys, one American and one not.

It opened old wounds for Allison, who left her life in New York to move to London where she and her wife could be married before 2013.

She was angry for a long time at the United States, she says, feeling like she was kicked out of her own country because she wanted to be with the person she loved. They built their life, had their first child. Stefania gave birth to Lucas using her own egg. At the embassy they were told he didn't qualify to be American.

"It all came flooding back and I saw all this anger and frustration and rejection," Allison said. "But this time instead of just being about me and about Stefania, it was about Lucas. And I don't want Lucas to ever feel the rejection and the anger and the hurt that I felt because of these things and because of the inequality."

Allison gave birth to their second child, Massi, with her egg, and he is American.

"If we had walked into the embassy that day and we had been a straight couple they never would have asked us to give proof," Allison said. "They never would have asked us whose eggs were they."

Now they have to think about things like how long Lucas can stay in the States when they visit family. The family physically separates in the airport: Stefania with Lucas in the line for foreigners; Allison with Massi in the line for Americans.

Andrew and Elad Dvash-Banks think about the same things. They can't get on a plane to see Elad's family in Israel because their son is on an expired visa. So the couples are suing for their sons — and also for the children of other same-sex couples.

Copyright 2018 NPR. To see more, visit http://www.npr.org/.