No fault divorce decree obtained abroad is not valid in India 

it should be on grounds recognised by HMA 

3) if divorce decree has been obtained on grounds recognised by HMA it would be valid in India 

4) you can file petition under section 7 of family court act for declaration that marriage is dissolved by US divorce decree 

It depends on the decree of divorce that was granted.

Law on this subject is if both submit to the jurisdiction of foreign court and seek divorce on any of the grounds available for them under Indian laws, it is valid.

 Since USA is not recognised by Indian Government as reciprocating Country, the Divorce decree obtained from USA has to be revalidated in the jurisdictional Indian Court.

1. They already invoked US court jurisdiction and obtained divorce decree. None of them raised the jurisdictional issue before the US court to hear the case. Therefore, the decree passed by the US court is valid one in India also.

2. If any one the party aggrieved against the US decree and want to contest the same in India then they can challenge the same in India under the ground that the decree was obtained by coercion and fraud. But, if both the party had sufficient opportunity to contest the case / contested the same on merits of the case then the decree cannot be challenged Indian court. Hope, I have cleared your doubts. 

If they have got their marriage dissolved by a court decree in USA for the marriage that was solemnised in India as per Indian laws, then it should be seen if the grounds by which the divorce was granted by USA court, if the same is not in conformity with the Indian laws then this divorce may not be held as legally valid, they may have to file a petition in India seeking divorce o mutual grounds once again

Since no system of private international law exists that can claim universal recognition on this issue, Indian courts have to decide the issue regarding the validity of the decree in accordance with the Indian law.

Note that, the US is not declared as a “reciprocating territory” by the Government of India, therefore it is mandatory to file a suit upon the U.S Divorce Decree.
Judgments from the U.S (non-reciprocating territories) can be enforced only by filing a lawsuit in an Indian Court for a Judgment based on the U.S judgment. The foreign judgment is considered evidentiary.

In case both the parties accepted the jurisdiction of a foreign country court and took divorce, the divorce decree is valid in India.

Any decree or order of foreign Court is valid and enforceable in India it is—

1. Pronounced by a Court of competent jurisdiction;
2. Given on merits of the case.
3. It is founded on correct international law and recognizes law of India.
4. Not opposed to principle of natural justice.
5. Not obtained by fraud, and
6. Is not against any Indian law.

If the decree of divorce  fulfils above conditions, it is  valid in India. There nothing more to be done in Indian Court.

Yes, a mutual consent divorce granted by foreign Court is considered as valid, legal and binding in Indian Courts by virtue of section 13 and 14 of CPC and also on account of comity of Nations, meaning tribunals in various countries grant probity to decrees of foreign courts. Such decree of divorce granted by foreign Courts need not to be validated in Indian Courts. Here in your cousin’s case, the divorce decree granted by the court in USA, is absolutely valid and legally acceptable in India.

Yes but same needs to be validated in Indian court

- As per law, a Mutual Consent Divorce granted by foreign Court is considered as valid, legal and binding in Indian Courts by virtue of section 13 and 14 of CPC and also on account of comity of Nations.

- Further, if the matter is contested between parties in US Court, and after due adjudication and trial, divorce is granted, then it will be valid and binding in India. 

- If the said decree of divorce is granted on the ground of mutual consent , then the said US decree is valid in India. and no validation required from Indian Court.