Written by: Aly Weisman | Feb. 13, 2013, 10:00 AM | 3,088 | 5 “Father of the Bride” Steve Martin, 67, and his wife, Anne Stringfield, 41, welcomed a child in December and have been spotted nearby their LA home with the secret new babe. “They’ve had a baby, and how they kept it a secret nobody knows,” a source tells Page Six. “Steve’s very…