Two US Citizens of Indian origin , Divorced after 20 yrs.498A

Hi, -- My nephew and his wife were Indian citizens and married 20yrs back in India -- Nephew didn't asked any dowry o gifts but his wife's parents said they gave her a gold chain/necklace, ring and couple of bangles and nephew has no idea about this -- Nephew went back to US after 2 weeks of marriage and his wife followed after two months after getting visa etc. -- Nephew helped her to get education/job , Green card and eventually both became US citizens. -- They have one major and one minor kids -- Got divorced after 20 yrs (initiated by wife and kind of forced it. ) -- Nephew came to know about her affairs during marriage as well as during the separation period. -- US courts granted divorce and perpetuity settlement. Wife's lawyer drafted the settlement as per wife's directions and nephew has no attorney. Its kind of outside court agreement in US. Now after the divorce and property settlement, both his wife and her parents are alleging he took her gold (as mentioned above) , demanding to return. But he is sure his wife has them as he never bothered about them. They are also threatening to file Domestic Violence,dowry, 498a etc. Can US citizens of Indian origin, married in India 20 yrs back, with the above circumstances , files cases in Indian courts? What is the impact on nephew , if travels to India. Can he be held/prosecuted by Indian courts? What is the role of US embassy/government?