Were you sleeping for 12 years? Now relax because your neighbor has 'adversely possessed' your land. You cannot evict him even if you file a civil case against him if he proves his possession for the last complete 12 years.
U file suit against him of illegal construction and also eviction suit claiming that building is urs and they r in illegal occupation without rent.if u once step to court automatically it take yrs to finish. He will come to compromise or fight in court. Don't bow for injustice .
Even if in your view the other family has committed a crime by occupying your land partially, but that imaginary crime they have committed 12 years before, so how the police will decide the section of the crime to help you in getting them convicted by the court which turned out to be 'adverse possession' permissible in law?