The two men married in Canada in 2009 and both of their names are on the birth certificates of their children, who were born via a surrogate mother, anonymous egg donors and both of their sperm.
But Italy doesn't recognize their marriage or dual parenthood. Under the law, De Gregorio is nothing more than a child care provider for Rubera's daughter, Artemisia, 4, and Rubera is considered the same for De Gregorio's twins, Chloe and Jacob, 2.
However, a bill now being debated in Italy's parliament could change those definitions, if it becomes law.
The bill, named after its author, Monica Cirinnà, only calls for the recognition of same-sex unions as "social formations." It falls far shy of allowing for gay marriage.
Both fathers' names are on all three children's birth certificates.
But it does, in its current form, allow for the legal adoption of stepchildren.
That means the Rubera-De Gregorio family of five could be legally related to each other and enjoy the rights of inheritance and guardianship, just as they do in Canada.
Rubera says marriage is important, but accepts that Italy won't move quickly to recognize his.
"We got married in Canada, so our vision for our project for life is with marriage," Rubera told CNN as he and De Gregorio fed their three children at their home in Rome. "At the moment, there is no possibility for equal marriage to be approved. I think we have to fight in the future for equal marriage. But at the moment, I think civil unions will be a good first step with stepchild adoption."
But the issue has divided even those who support same-sex unions.
Many people who support same-sex unions for tax benefits and inheritance do not support the adoption of children by same-sex couples.
Costanza Miriano, a married mother of four and the author of two books on traditional family values that have been featured by the Vatican's L'Osservatore Romano newspaper, believes that same-sex couples do not have the right to have children.
"Children have rights," she told CNN. "And the first and most fundamental right is the right to have a father and a mother."
Divided Church
The debate is echoed in Italy's parliament, where the bill is expected to pass, but not necessarily with the article on adoption. That could be dropped in a compromise, or even put to a referendum sometime later.
Those supporting the new legislation held rallies in more than 80 cities across Italy last weekend, drawing massive crowds. Marchers carried clocks to underscore the theme "wake up Italy."
On Saturday, the Italian Bishops Conference and several groups opposing the legislation will hold their own rally at Rome's Circus Maximus. A heavy turnout is expected.
Supporters and opponents of the issue, however, are not divided strictly on the basis of religion.
Even within the Vatican, there are high-ranking bishops and cardinals on both sides of the debate.
"We must never forget the identity that is proper to the family, its importance for the country's stability and economic development, and its key role in the education of the new generations," Angelo Bagnasco, the president of the Italian Bishops, said ahead of this weekend's Family Day march.
But Nunzio Galantino, secretary general of the Italian Bishops and a close ally of Pope Francis, has a much softer tone.
"Society has in itself an increasing presence of different kinds of couples," he said in a statement. "The State's duty is to give answers to all, with respect to the common good, above and beyond the welfare of single individuals. We are all learning that when confronted by such a complex reality as this, if positions are radicalized, whatever the good will, one ends up with fragmented and disorderly solutions which are often the product of the prevailing of one lobby over the other."
The debate in parliament is no less divided, with some who oppose it even publicly tweeting that civil unions are akin to a man marrying his dog.
"They portray us as robbers or kidnappers, using words like 'womb for rent, uterus for rent,'" Rubera told CNN. "Saying you stole your kids, you stole your kids from their mother. You denied to your kids to have a mother, you bought your kids from the supermarket like watermelons ... So it's difficult to imagine if you aren't living in Italy, not living this situation, how strong and awful the public debate about civil unions has become."
