Gift Deed of father self acquired property by mother

We are a family of 6 kids (4 daughters-{1 has passed away} and 2 Sons). My Father had a property(with 2 floors) in bangalore and he passed away a long time ago, after which the property was transferred to my mother. 5 years back, the 2 sons got a gift deed executed in their names for their respective floors, without even informing/considering the daughters. We became aware of this activity couple of days back.Now, though my mother is still alive, since both the sons are having frequent conflicts, they are thinking of selling the property.Wrt the above history, I need advice on the following- 1. My father earned this property on his own and it is not ancestral. Do the girls have any share whatsoever in the property?2. Can such a gift deed be executed by my mother without our(daughters) consent/consideration . Is it Valid? Can the daughters still claim for their share in it.3.Now that the gift deed is done and they are trying to sell the property, Are our signatures required to sell