Is my mother’s Will valid and can my brothers contest it?

I am from a Muslim family in Kerala. My mother passed away in 2011 and left a Will stating that her property would be given to me after her death. She had three sons and one daughter (me). At the time of writing the Will, the other sons had no objection to me receiving all her property. However, now, years later, two of my brothers are claiming the Will is invalid for a Muslim and are demanding that the property be divided. Is it true that the Will is invalid and I cannot claim the full property my mother willed to me? Can my brothers challenge the Will? If so, how will the 38-cent land be divided among the four children (three sons and one daughter)?