Answer
Ratan Tata was born as Ratan Naval Tata, the son of Naval Tata and his wife Sooni. Naval Tata was the second son of Ratanji Tata, who had adopted Naval's father, Hirachand Tata, and had changed his name to Ratanji Tata. So, Ratan Tata's biological father was adopted by Ratanji Tata, and his adopted father was Naval Tata.