While Rakesh Roshan and Rishi Kapoor have shared a warm relationship right from their acting days, not many know that their sons- Hrithik and Ranbir- too are extremely close buddies. The two actors grew together and have shared a close bond ever since. In fact, sources say that Hrithik being the eldest of two also used to take special care of Ranbir. Our source reveals that Hrithik also used to baby sit Ranbir Kapoor when the latter was just four years old. How cute, we say. When Ranbir Kapoor made his debut with the Saawariya in 2007, Hrithik was the first one to call and congratulate him. Hrithik had then predicted that Ranbir would go on to become one of the biggest superstars of the country and how true those words have turned out to be. Says our source, "Hrithik and Ranbir have shared a great equation over the years and have been friends since their childhood days. Till date Hrithik calls Ranbir after every film to give him feedback on his film performances as well as his commercials." Well, we think perhaps it is time to extend their off screen rapport to the silver screen as well by starring in a film together. With their combined star power, we are sure it won't be too difficult to pull off a 100-crore blockbuster in record time.