Looks like we have 2 theories for what is going on.
Theory #1 is someone is out for Akshay and family's lives. They killed Akshay because of the secret he carried.
1. Janki Devi
Motive - wants to keep Kajal out of Raunak's life. Cannot afford to lose her son to her past deeds 5 years ago. Will go to any lengths to ensure the truth isn't revealed and possibly out of desperation arranged to have Akshay killed. Did not expect that Raunak and Akshay would be in the same care that day.
2. Munmun
Motive - wants to be in Janki's good books. Wanted to get rid of Akshay for Janki so she doesn't have to worry about what happened 5 years ago. With Akshay out of the picture everything would be fine. Did not expect Raunak and Askhay to be in the same car that day. If she isn't the murder I would believe she and Kaamini would be at least accomplices to Janki's plans.
Theory #2 is someone is out for Janki and her son Raunak. They intended to kill Raunak and did not account for Akshay getting in that car that day.
1. Vidhi
Motive 1 - wants to get rid of Raunak as that is Janki's strength. Without him Janki becomes an easy target. She is tired of living under the thumb of Janki and Raunak. She and her children have to receive "permission" to do anything . She wants the property rights for her children as well.
Motive 2 - what if she was the woman that Janki's husband was in love with. They were suppose to get married but the Janki changed circumstances to which Vidhi ends up having to married the younger brother. Vidhi is out for revenge to what Janki did.
2. Vidhi's husband
Motive - tired of living under the thumb of his sister-in-law. Janki treated his brother really badly. Everyone just thought Janki was the victim. He is getting revenge for the way his brother was treated and how he and his wife are treated. They want their property rights.
3. Raunak's cousin (the girl cousin) - she is tired of being treated like second class in the household. She wants to get rid of Raunak and Neeti.
4. Neeti - she is tired of being put second by her mother Janki. She wants to get rid of Raunak so Janki will pay attention to her. Or she just wants to get rid of both as they are annoying and she can then live her life the way she wants to 😆
5. Janki's brother - he is tired of his bossy sister. Wants to get rid of them both so he can live his life peacefully 😆
I personally am starting to think it is Theory #2 and Vidhi is probably the most likely culprit now. As much as Janki is bad I sort of don't want her to be a murderer at least in Akshay's case. I think it would be far more interesting if it is someone else and Akshay's death was an accident. The real motive was to kill Raunak to get to Janki.
This gives more layers to the story. If Kajal saves Raunak and Janki then Raunak's respect for Kajal will only increase. And the love will only grow stronger on Raunak's side. Janki will be slightly indebted to Kajal. I don't think she will accept her wholeheartedly but she will have to at least tolerate her.