This is the 34-year-old actress' first child with her musician boyfriend John Kastner. The proud father introduced the newborn on Instagram, reported Ace Showbiz.
"Please meet Blues Anthony Pare Kastner...," Kastner captioned the picture.
The baby bundled up in a blanket was seen being held by his equally-adorable big sister Summer Lee, Kastner's eight-year-old daughter whom he shares with former wife Nicole de Boer.
Pare who played Megan Draper on the AMC series started dating fellow Canadian John Kastner since around 2012. She announced she's expecting their child in October 2014. She was previously married to writer and producer Joseph M Smith. They have no children together.