Today Shanatnu gave a very creepy smile at Vaishali after making her very emotional.
Can this be possible that Shantanu is the biological son of the nurse, whom Vaishali gave away her own son. His mother may be giving some special attention to the Purohit son and he would be feeling jealous about it then and so now has come back to take revenge on this family due to whom, he had to share his mom's love.
A person who has undergone all the trauma which he stated cannot become so creepy and rejoice immediately, even when he is a grey character. He can only do it, if he is simply using some other's trauma for his benefits.