Watts and Schreiber in 2007
12/15/2008 at 07:50 PM EST
and Liev Schreiber have revealed more details about their newborn son
, starting with his name: Samuel Kai Schreiber.
Samuel – the couple's second child after year-old son Alexander Pete Schreiber – was born Saturday and weighed 7 lbs., 13 oz., the couple's rep tells PEOPLE.
"Both mom and baby are doing great," the rep says.
Reporting by LIZA HAMM
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