1) If you are apprehensive of your lawyer changing sides, change your lawyer.
2) Surprised to know that your case is running for 17 years.
3) if you have filed the criminal case against the sellers and the brother probably by this time the criminal case and the civil case would have been completed long long ago. Not sure on what was your legal strategy when the issue came up.
4) If you can provide me us the Docket Order of your court case, we will be able to tell you the exact remedy for speeding up the court case.
5) In your case, the other side knows that they will loose the case and hence probably have been dragging the case for such a long time so as to harass you.
6) Also we presume, you are in possession of the house and also that the property is mutuated in your name in property tax, electricity bills and water connection etc.
hope this helps.