Jaidev, Bal Thackeray's estranged son, is currently being cross-examined by the lawyer of his brother and the current Sena chief Uddhav Thackeray.
Jaidev has challenged Bal Thackeray's will which does not give him any share in the property.
Aishwarya is part of the will and got a share of property.
To a question about his movements between his flat and the Thackeray residence 'Matoshree' in suburban Bandra, Jaidev said post 2004, he stayed on the second floor of Matoshree whenever he visited it, since the first floor was occupied by "some unknown person".
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"Is Aishwarya your son?" advocate Kapadia asked.
"No, he is not. In fact, I have wanted to set the record on Aishwarya's paternity straight for a while now but have not got a chance," Jaidev said.
At this point, Justice Gautam Patel restrained Jaidev from elaborating and the court adjourned for lunch break.
Jaidev had told the court earlier that he moved out of Matoshree in 1999 due to the increasing discord with Smita. Smita continued to live in Matoshree until their divorce in 2004, and during this period he regularly visited his father during the day but returned to his flat at night.
These visits stopped only a month before senior Thackeray passed away in November 2012, Jaidev said.