It’s official! Rachel Bilson and Bill Hader made their public debut at the Golden Globe Awards on Jan. 5, just two months after the unlikely couple were first linked together. “It felt good to bring their relationship out in the open,” spills a source. “This isn’t just some winter fling. Bill and Rachel are truly in love and things are getting serious. They’ve already introduced each other to their children.” The Hart of Dixie actress, 38, shares 5-year-old daughter Briar Rose with former fiancé Hayden Christensen, while the Barry star, 41, has three kids — Hannah, 10, Harper, 7, and Hayley, 5 — with his ex-wife, director Maggie Carey. “Though it may seem like they’re moving fast,” the source admits, “this is a second chance at love, for both Bill…
