Barring the invincible Shah Rukh Khan, all the big stars in demand seem to be scions of film families.

From the super-exclusive Aamir Khan to the viewer-friendly Vivek Oberoi, from the brooding Ajay Devgan to the exuberant Salman Khan, the really hot faces and names are all star sons, ready to storm the box office.

The latest claimants to have hit pay dirt are Abhishek Bachchan and Saif Ali Khan -- interesting studies in contrast who come together in another star son director Rohan ("Kuch Na Kaho") Sippy's next film. Abhishek and Saif have delivered surprisingly successful performances within a week of each other.

Abhishek's role as the goon Lallan in "Yuva" has won him rave reviews from all quarters and put him right up there with the big guns.

Producer Ramesh Sippy, who has just signed both father and son, for separate films says, "The busiest actor in Mumbai is Amitabh Bachchan. The second busiest actor is his son. And this, in spite of the fact that cynics say the younger Bachchan hasn't delivered any hit!"

How does one explain the fact that Abhishek was working three shifts per day even without "Yuva" to his credit? Pedigree? But if it was only that, Dev Anand's son Suniel and Rajendra Kumar's son Kumar Gaurav, too, would have been around long enough to finally serenade success.

"No, things have changed," says bright young filmmaker Hansal Mehta. "Directors feel star kids have it in them to deliver performances. Unlike newcomers or rank outsiders, these star children instinctively know the ropes. Hence Abhishek and Kareena remained superstars although their films failed. In fact, I was very keen to work with Abhishek but he didn't have dates for me."

Now with Saif Ali Khan joining the star-ranks after the surprise success of his solo hero film "Hum Tum", even heir apparents of actresses seem to have finally broken through. Legendary actresses Nutan and Vyjayanthimala's sons (Mohnish Behl and Suchindra Bali, respectively) couldn't find much success.

But now things seem to have changed. Sharmila Tagore's son Saif, who had so far been given the status of superstar among supporting actors, has surprised everyone by climbing out of his stipulated circle of success.

"Hum Tum", which came to Saif by default after the first choice for the role backed out, has shocked many trade watchers with its box office performance. The film beat the multistarrer "Yuva" opening collections by registering a 100 percent opening in Delhi, Mumbai and several other cities.

In a place like Patna where urban films like "Kal Ho Na Ho" and "Hum Tum" are considered non-viable commercial propositions (in fact Yashraj Films was toying with the idea of not releasing "Hum Tum" in smaller centres), the film has not only opened well but actually improved its collections in the second week!

In the US, "Hum Tum" collected a whopping $400,000 and in Britain it made 450,000 pounds during the first week -- almost putting it on par with the opening week collections of a Shah Rukh Khan starrer.

How do we explain the success of "Hum Tum"? It's of course urbane witty, sassy and savvy. The humour is tailored to college-going youngsters all over the world who believe in romantic banter as the some total of romantic existence.

But there's more to the success of "Hum Tum". And it's the scion factor. Hindi audiences all over the world have begun to look on star kids as screen-friendly and engaging chips of the old block.

With Abhishek and Saif finally arriving at the top, other star kids like Raj Babbar's son Arya Babbar and Jeetendra's Tusshar Kapoor who are struggling to find a foothold have begun to get hopeful again. Pedigree pays after all.