January Jones took her adorable son Xander for a stroll in Beverly Hills over the weekend, and the typically stone-faced Mad Men starlet couldn't stop smiling!

But we're still dying to know ... who IS Xander's daddy? January still hasn't dished the deets on who fathered the child or whether he has a relationship with the tiny tot. Not like it's any of our business, but when your ex is Jason Sudeikis and your kid looks just like him, we have to wonder!