Look at those cheeks! James Marsden spent at least some of his holiday weekend with a very special little guy: William Luca, the baby boy he welcomed with ex-girlfriend Rose Costa back in December. In the first-ever glimpse of his son, the 30 Rock actor pushes a stroller with one hand and holds William -- pouting contemplatively with a baby-blue cap -- in another.

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William is the third child for Marsden, who shares kids Jack and Mary with ex-wife Lisa Linde. Linde filed for divorce from the X-Men star in September 2011 after 11 years of marriage; Marsden and Costa dated briefly following that split, with reports of her pregnancy surfacing last June.

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The handsome star also became a dad again recently on the small screen: On last December's series finale of 30 Rock, his character Criss Chros and new wife Liz Lemon (Tina Fey) adopted two kids.

This article originally appeared on Usmagazine.com: James Marsden Debuts Baby Son William: Picture