Can a child born out of an illicit affair claim share in the property

My father married 2nd time with out anybody's notice and has a girl child with that relationship. Now that girl child is major and doing job and unmarried. Will she be alegal hair for my father's property? All the property my father has is of ancestral property. Nothing is self generated. My father stays with us only. Simultaneously he maintains other home. His second wife was well aware of his 1st marriage and me. Still went on to marry him about 23 -25 years ago. We came to know about it recently. How can i hold our property with out letting her claim her rights? Pls advise. Our religion Hindu