A married lesbian couple on Thursday asked a federal court to force Pennsylvania to recognized their Massachusetts marriage.

Isabelle Barker and Cara Palladino married in Massachusetts in 2005 before moving to Philadelphia later that same year when Barker got a job at Bryn Mawr College.

“My Massachusetts marriage certificate is the same as any other couple that comes from Massachusetts,” Palladino told reporters during a news conference overlooking Independence Hall. “It seems to me that that's the essence of discrimination. If you're taking the same piece of paper and you're treating it differently because of our status, that doesn't seem fair.”

Barker said that the couple's four-and-a-half-year-old son has begun asking whether his parents are married.

“And it's sort of befuddling to us that we don't have a really clear answer for him about that,” Barker said. “If we lived in Massachusetts, we would have a very easy answer: 'Yes, of course.'”

The lawsuit names Governor Tom Corbett and Attorney General Kathleen Kane as defendants and was coordinated by the Equality Forum, a Philadelphia-based LGBT rights group.

“Since the inception of the nation, almost all marriages sanctioned by one state have been accepted by all other states,” said Malcolm Lazin, executive director of Equality Forum. “Failure by Pennsylvania to recognize a legal marriage denigrates Cara, Isabelle and their son and denies them important family protections and benefits.”

At least two additional lawsuits have been filed challenging Pennsylvania's marriage ban.

(Related: Second lawsuit filed challenging Pennsylvania's gay marriage ban.)