Can Children of 1st wife claim share in 2nd mother's property ?

my dad has 2 children from 1st marriage and got divorced 40 years back. And now 2 marriage 3 children's including me.and now my question is that my mother 2 wife have got property purchased within span of ten years so do children of 1st wife can claim share in my mother's property in future. My mother doesn't want to give any share to children of first wife and she wants to write will in our name (3 ) children. Will the will be a valid document in future.