"I do not know. I may be the next target of my mother. She is very powerful and she can do anything she wants," Mikhail Bora told reporters in Guwahati.
"I can go to Mumbai only if the Assam government ensures that two nurses take care of my (ailing) grandparents here," he said.
Indrani Mukherjea is the wife of former CEO of INX Media, Peter Mukherjea. Sheena Bora and Mikhail Bora are her children from a previous relationship and were raised by their grandparents in Guwahati.
On Wednesday, Mikhail Bora revealed that Sheena was his sister, that Indrani had mothered both of them and this could be easily be proved by a DNA test.
A two-member team of Mumbai Police arrived in Guwahati on Thursday to get further details about Sheena Bora and the family.
They went to Indrani's parents' house where Mikhail Bora lives.
Mikhail Bora said he knew the reason why Sheena Bora was murdered and he would reveal it after August 31 if Indrani Mukherjea does not volunteer to tell the truth.