To answer your question Ansh was really evil, he married and raped Nandini who was in love with Karan and Bhoomi is his and Nandini's daughter. Ansh was also responsible for the murder of Shobha's first husband Vishal. Ansh had also been married previously to a woman named Shraddha and had abandoned her and his son Eklavya. Tulsi killed him because he was so evil and was hell-bent on destroying Nandini's life even after she had finally married Karan. Tulsi also brought Eklavya home, everyone was against accepting Eku so Gautam-Damini adopted him. Tulsi has hidden this from the new generation because she wants to let sleeping dogs lie, and doesn't want to remind everyone of the atrocities committed by Ansh, especially Eku who already matches Ansh in the looks department. Damini-Gautam have two kids of their own who are twins, Nakul and Mayank. Mayank is mentally retarded and Ganga adopted Nakul. Actually both Ganga and Damini were pregnant at the same time when both met with an accident. Ganga lost her kid but saved Damini. Ganga sort of went crazy after she came to know she had lost her kid, so Damini let her adopt one of her twins.