I think Raj loves Tanya, not Trishna...
Becoz as we know among the sisters, it is not Sujata(as he is supporting Raghav-Sujata) or Mansha(as she is too young for him)...
When Mansha went into kitchen to help him, he said that gradually love will happen but he will not tell the girl's name which Mansha assumed Trishna in her mind...
Now when Trishna was getting ready to meet Raghav's parents for her proposal... He was upset becoz nobody seemed to be happy with this proposal...When Trishna was about to explain him that what others are thinking when a boy becomes upset that a girl is getting married then suddenly someone called her and becoz of the conversation cut short, Raj could not understand what Trishna & others meant by his behaviour towards Trishna's proposal...
Also they have not shown any specific or exclusive one-to-one conversation between Raj & Tanya unlike the conversation with Raj & other 3 sisters like Raj-Sujata about Raghav, Raj-Mansha in kitchen and Raj-Trishna always....
Mrs. kohli was also repeatedly shown praying to god that Raj should be her son-in-law and Trishna should agree for this marriage..But she never said Raj-trishna marriage should happen...
I think a great twist is coming... Maybe Raj loves Tanya but then we will see that Trishna will fall for Raj...On the other side, Kanhaiya is also there torment Tanya...
Guys, this is just my assumption...