The couple's new arrival was due in March (11) but his timing was perfect for Guarini, who wrapped his role in Broadway's American Idiot musical on Sunday (24Apr11).
He tells People.com, "Quite a polite fellow for waiting until late Monday, early Tuesday to make his entrance. With a full head of curly brown hair, wide open and alert eyes he came charging into the world.
"Reina is doing wonderfully and should be given a medal for going 10 months and 1 week with child."
Funnyman Kevin James, Black Eyed Peas star Taboo and former Beverly Hills, 90210 star Ian Ziering have also become dads in the past few days.