Going through Contested Divorce (8th year)

I'm a Hindu married to a Sikh. I filed for Divorce in 2012. And the case is still pending before the Court. I also have a son who is now 7.5 years old. We have a flat which is a joint property. I'm the main owner, and my soon-to-be-ex is the Co-owner. Out of goodwill, I added him as a Co-owner. We never marry expecting a Divorce later. And because of it, I'm going through hell. 7 years of marriage was hell. My father and I have majority of contribution towards this flat. We got separated in 2012. And since then, I have been paying all the EMIs toward this flat. We bought the flat in 2010. And the EMI was less back then because it was on fixed interest rate for 2 years. Though he was living there with me, he wasn't regularly contributing toward the EMI. After we got separated in September, 2012, I have been bearing the EMI of5 lac rupees per annum. He had not contributed anything.Yet he is asking for share.He has got a duplex apt hich he co-ownerns with his brother & father. Pls advise.