Rob McElhenney and Kaitlin Olson

It's Always Sunny in Philadelphia co-stars Kaitlin Olson and Rob McElhenney have welcomed their second son, People reports.

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Leo Grey McElhenney was born at 1:15 a.m. on Thursday at the couple's Los Angeles home. The new arrival weighed in at 8 pounds, 5 ounces and joins older brother Axel Lee, 19 months.

"We are overjoyed," Olson, 36, and McElhenney, 34, tell the magazine. The couple, who starred together on It's Always Sunny for seven seasons, married in September 2008.