1. At the outset you are advised against taking any quick step since patience is the key word in such cases and hurried step may mess up the matter completely. Having extra marital relationship during the pendency of marriage is a punishable offence, if proved. So, exercise restrains to ensure that the wife of your paramour does not lay hand on any document evidencing his relationship ( specifically physical ) with you,
2. Your man shall have to file a divorce petition on the ground of cruelty submitting adequate evidence in support of his allegation,
3.If the said divorce case is contested by his wife it may take 2 to 4 years to be disposed of and till then you shall have to wait with patience,
4. After receiving the notice for divorce case, his wife may retaliate by filing 498A complaint, DV case seeking maintenance etc. for which your man should be prepared fully,
5. You can legalise your relationship only after his getting the decree of divorce from the Court.