Do the children need step mother when their mother dies?

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when a married woman having some children dies due to some reasons while her children are small and helpless, her husband brings a new mother to take care of those children. But actually what happens that the step mother behaves those helpless children very rudely and cruely.But their father doesn't speak word in fovour of his children.Finally those children, some run away from home to become street children while some struggle as an orphan though they have a living father. So, i want to ask if there is any need of step mother for the motherles children or not.