How can we enforce the Sharia Law and the fatwa issued by Darul Ifta to ensure the child’s custody?

Asalam alaikum, My eleder brother expired two years ago leaving behind a wife and a minor child. After some period of time recently, the widow (wife of deceased) got remarried. In this point of view we went to Darul Ifta in Hyderabad to know the Sharia Law for the child custody in such situations. They gave us saying that the Child if female shall be with mother and if male then after her remarriage the child until the age of 7 should be with the maternal grandmother if she is alive and later after 7 to the paternal grandparents if she is not alive then the custody shall be for the paternal grand parents. Now the problem is we have been seeking from the widow the custody but they are reluctant to give when we show them the fatwa they told us to keep it aside and they want to have the share from the property (the share of the widow). we have no problem in giving the share we evaluated as be the sharia law and gave the figure how much will it be and later they keep on delaying things with the intention to avoid the cutodial issue of the child. Until now the issue is pending so far we havent seek any assistance from the court. we would like to seek your kind assistance is doing the rightful. Please guide us, and show us path to safegaurd the childs mental conditions as t he mother (widow) took the child with her to his new husband. Guide us how can we enforce the sharia law, the fatwa issued by Darul Ifta.