Settlement deed

We live in chennai. My father has settled the chennai property self acquired, to my mother 10 years back. Mutation of records have taken place on my mother's name. Me my mother and father currently live in this property for last 13 years. Now the issue is my father has a family before my mother. He has not divorced but married my mother. In legal terms the marriage between my mother and father is null and void. Whereas in settlement deed he has mentioned my mother as wife and out of love and affection he has settled the same to her. My father has three sons from first family. Can they create issues in the future regarding this settlement deed.