While mobs of fans are taking a whack at guessing how the season finale of The Sopranos will end Sunday night, there's a bigger mystery brewing:

Are the actors who play Meadow Soprano and Jackie Aprile Jr. dating off-screen? 

While Jamie-Lynn Sigler and Jason Cerbone's on-screen romance appears to be sleeping with the fishes after Meadow caught Jackie with another woman, the pair are reportedly steaming things up in real life. 

The sultry 20-year-old brunette actress from Jericho, L.I., and the hunky Cerbone, 23, of Yonkers, have been spotted in recent days canoodling at Manhattan nightspots. 

The Post's Page Six reported Wednesday that the two red-hot Sopranos stars were openly liplocking at Tom's Bar at the new 60 Thompson Street Hotel earlier in the week. 

"They were kissing right at the bar," a source said. 

A week earlier, Sigler - who just ended her run at Madison Square Garden in the musical production of Cinderella - and Cerbone came off "like kids on a date" while dining for two at the West Village's Blue Hill restaurant, the New York Observer reported. 

Spokesmen for both actors insist the pair are just good-fellas. 

"They're very good friends," said Cerbone spokesman Jonathan Chaben. 

"They hang out a lot. They play around and go dancing, but there's nothing romantically. Jason is dating someone, anyway." 

Meadow is the intelligent but wayward daughter of mob boss Tony Soprano, while Jackie Jr. is the mixed-up son of Tony's former boss, who died of cancer in the first season of the HBO hit series. 

Sopranos fans have placed Jackie Jr. at the top of the "hit" parade, with many speculating he won't survive Sunday night's season-ending episode after robbing a poker game run by Tony's wiseguys. 

Another character who could find himself sleeping with the fishes is Paulie Walnuts, the target of the Russian mob, and maybe Tony, for placing the family in harm's way with the Russians.