Rob McElhenney says he's pro-gay marriage and was partly raised in a gay family.

McElhenney spoke to GregInHollywood.com's Greg Hernandez about the upcoming fifth season of FX's It's Always Sunny in Philadelphia and his support for gay marriage.

“I happen to be pro-gay marriage,” McElhenney told Hernandez after a session at the TV Critics Association Summer Press Tour held in Beverly Hills. “I was raised partly by two gay mothers who have a domestic partnership in New Jersey.”

The 33-year-old actor said the first two episodes of the new season tackle the difficult subject of marriage equality.

In the episodes, a transgender woman (played by Brittany Danke) ditches Mac (McElhenney) to marry another man.

“My character decides that he is going to fight their union in court because he feels it's a gay marriage,” McElhenney said.

“Dennis (Glenn Howerton) also gets married. And that is sort of the satirical look at marriage in this country and how difficult it was for Carmen, the transgender woman, to wind up getting married.”

“And Frank (Danny DeVito) and Charlie (Charlie Day) end up getting a domestic partnership to get health benefits and it's a very difficult road that they're going down,” he added.

It's Always Sunny in Philadelphia returns to FX on September 16.