2.Urmila Matondkar: Remember the cute little girl in Masoom? That's the rangeela girl Urmila. She was with another child actor Jugal Hansraj, but thankfully has fared better than him in her adult roles. But her debut was Kalyug (1980) where she played the role of a boy. She has also played son to Rekha and Raj Babbar in Parikshit
3. Kunal Khemu: The cute little kid from many hits (and flops) of the 90's is what Kunal Khemmu was earlier identified for. Some of his movies include Hum Hain Rahi Pyaar Ke, Raja Hindustani, Zakhm.
4. Hrithik Roshan: Before being the benevolent Akbar, Hrithik Roshan played a few roles in his father's films (a habit he has maintained still) like Aapke Deewane and Bhagwan Dada. Duggu then moved on to assisting his father as an assistant director on Karan Arjun and finally made a roaring debut with Kaho Naa Pyaar Hai.
5.Aamir Khan: Bollywood's answer to perfectionism found his way into films really early when he acted the role of the youngest brother Tariq in Yaadon Ki Baarat. There is also a song and dance sequence where he raises his little finger, indicating that he had to answer nature's call. Aamir also acted in Madhosh (1974).
If it have been posted before, sorry!
12