Maintenance claim for minors

Sir, A friend died in 2008 leaving his wife and 2 daughters without any income. His wife took her kids and left maternal home in 2010 due to family problems. She has no income and kids were supported by her parents. Recently her father in law died. Her mother in law and sister in law forged a will and are in possession of business and all other assets. What's the best way for kids , to file maintenance suite or to file a private complaint on forgery and later partition suite?