Desertion Case Along With Live In Relationship

This query is on behalf of my sister. She was married 10 years back. She is a working professional. Had taken a job In middle East 3 years back. Now when she come back and is working in India, husband is working in another city and it is putting false allegations of illegal relationships on her and wants to get separated. He later himself accepted of being in another relationship and staying with other unmarried Hindu girl as live in. For separation since my sister wants to move on she agreed but only after transferring all properties in her name. My sister had contributed a majority chunk to the 2 properties. Initially her husband agreed but now he is demanding a share of the property. Is it allowed for him to be in live in while my sister is alone and feeling cheated. Can he demand a share of property if there is enough evidence from the bank statements that his contribution was minimal and he was in the relationship only for having a lavish lifestyle?