Property Law

My dad was married to a women he had 3 kids. He then married my mother ( second wife) and has one daughter. We are hindu. My dad purchased a flat in 1994. He made an affidavit stating that the flat should be transferred on my mother's name ( 2nd wife) . the affidavit was made in 2004 with 20rs stamp paper it's also been notarised. My dad died in 2005. Now after 15 years the 1st wife has made that flat on her name. Can my mother still claim that flat on the basis of affidavit ? The 1st wife didn't take any noc from me ( daughter of 2nd wife) . Can I also claim my share in that flat ? what should be done ?