Nidhi jumped to death after pushing her two children from the 19th floor from her residential building in Malad on March 8. police said.
"Nidhi's husband Pawan Gupta was arrested from the city today. We are looking for other family members. Earlier Nidhi's sister-in-law Sunita was apprehended on Friday," said Vinayak Kakade, senior Inspector at Dindoshi police station.
Pawan held on the charges of abatement to suicide and torture has been remanded to police custody till March 21, he said.
Nidhi, a chartered accountant and professor, allegedly hurled down her son Gaurav (6) and daughter Mahika (3) from the 19th floor of the 21-storeyed Sahyadri Housing Complex before jumping herself.
She had been married to Pawan, who is into a ready-made garment business, for 10 years. A suicide note left by the victim reads "nobody is responsible for this", police said.
Nidhi stayed with her husband Pankaj and his family members comprising in-laws, brother-in-law and sister-in-law at a flat on the 9th floor of the building, they said.
Nidhi’s father Bimal Jalan had registered a complaint against her husband Pawan and in-laws on Friday.