Vijaybhai Vaghasia, 32, his wife Rekha Vaghasia, 30, and son Veer Vaghasia, 4, died in the incident.
The couple, who lived on the second floor of the Majestica building, threw the child from its 12th floor terrace and jumped down themselves, police said.
Vaghasia's cloth shop had recently shut down, and police said he and his wife may have taken the extreme step due to a financial crisis.
No suicide note was found.
"Primary investigation has revealed that Vijaybhai was facing a financial crisis," said an officer from the Sarthana police station.