1. Typically he is not bound by any such Notice.

2. What should have been done is a Police FIR, for Rape, Molestation, Breach of Trust, Intimidation, Cheating etc.... supported by all possible relevant documentary proofs and witnesses. This would be successful and the boy would come down for settlement.

 - As per the Supreme Court,  When a man and a woman live together as husband and wife for a long term, the law will presume that they are legally married unless proved contrary.

- Further, the Protection of Women from Domestic Violence Act 2005 provides for the protection,maintenance and right of palimony to a live-in partner, if she complains.

- Since, your sister was having relationship for 9 years , then she shoud take legal actions against him.

- Further, as she has already send him a legal notice , but she should not wait for 15 days of time , as advised by the  lawyers.

- Without any further delay , she should lodge her complaint against him before the police and higher official , after mentioning all the facts in details, and specially that he has cheated her on the pretext of marriage. 

- Further , if police refused to lodge an FIR against him , then she should also file a complaint before the magisterate  

If he fails to marry your sister file case of rape and cheating against him under section 376, 420 of IPC 

your sister had sex with him under promise of marriage 

3) her lover can marry another girl 

4) it is not an offence 

Yes the action can be taken on breach of promise marry later also. 

Sending notice and mentioning any time was your biggest mistake.

By this you made this a civil dispute.

Anyway if you want to make this man taste rigours of law then lodge a complaint of rape u/s 376 IPC as sex on the promise of marriage amounts of rape.

Dear Concern,

Please note - 

01. Can the concern marry any person of his choice?

Answer - Yes. Anyone can marry anyone as per his or her choice despite being in relationship with other person for a long period of time. 

02. Can you do anything about it?

Answer - No. You can't stop anyone from getting married unless you are legally wedded husband or wife of the concern and he or she is trying to contravene the law. 

03. Can you bring case in against the concern for not agreeing to marry you?

Answer - Yes if you can prove that the opposite party was trying to play along with you and never had any intention of having any sort of lifelong relationship with you under section 406 of the IPC which is Criminal Breach of Trust.

If he or she threatens you to spoil your name, repute etc then you can also bring a case under section 506 of the IPC which is criminal intimidation.  

If he or she publishes personal photos or videos or both of yours which are derogatory in nature then you can bring cases of obscenity in against the concern. 

04. Can you seek damages from the concern under the head of mental harassment under Civil Law?

Answer - Yes

05. Can you bring case for maintenance and domestic violence in against the concern under Domestic Violence Act?

Answer - Yes provided you can prove that you were living together as a husband and wife (live-in-relationship).

06. Can you bring the case of rape in against the concern?

Answer - Yes but you will not succeed in that case as consensual sex do not amount to rape. The Hon'ble Delhi High Court has recently passed an order covering this aspect of relationship in between two adults. 

07. Can you stop the concern from getting married to someone else in a situation like yours?

Answer - Yes, provided you prove that you both were in live-in-relationship. Law recognizes live-in-relationship as a relationship which is equal to living together as a husband and wife.   

This case would be a tricky one and you need to contest this case (if you want to) with special caution in consultation with some very good advocate.

My best wishes to you.

You can file case under live-in-relationship and tort law that breach of promise to marry is done by her friend.

The offence punishable under sections 376 and 420 of the Indian Penal Code, 1860.

She has to first lodge a criminal complaint against him for cheating  her and having sex with her on the promise of marriage whereas now he is denying to marry her.

The courts can punish him up to 7 years of imprisonment if found guilty for the said charges.

She can include rape charges also in her complaint and follow it up properly through the police to get him booked immediately and pushed inside.

See anyway the person can marry other women even if your sisters files a police complaint . See your sister has only option to file police complaint of rape against the said person as he obtained her consent for physical relationship on false promise of marriage.

He can be punished for same though cannot be forced to marry.

Promising to marry and then having consensual physical relation amounts to rape, keep the FIR draft ready, if you find the guy getting married, lodge it immediately then and send police as a gift to his marriage

Dear Sir,

You have two options, one is to approach immediately to police and stop him from marrying any other girl. Secondly, you may approach Civil Court and file a suit for permanent injunction and get interim stay order on the first day of filing the suit. You are sister can also file a complaint against him alleging offence of rape and breach of trust etc..

Judgement by SC in this regard is very peculiar and partially half backed. 

It would be very difficult to prove in many cases the promise made was false at the very beginning to construe the physical relationship as an offence of rape and cheating. 

This judgement is controversial. Other bench of SC had taken partially different views. Accordingly an educated and modern society women very well know about, the uncertainty of such promises, and the modern life style and therefore they can not said to be cheated by breaking of the promise of marriage .

Talk in details with your lawyer. Police can take FIR. This is not a big job. But it may be difficult to prove first the promise itlsef was made out and then it was false at the very beginning.

I already told you this judgement is partially half backed and both parties are getting into trouble due this judgement. 

She can file FIR of rape and cheating that on the pretext of marriage he made physical relation with her.

Victim can serve legal notice to her bf in initial stage and if not getting any proper response from him then can go to lodge an FIR against him. Victim can lodge FIR when she deems that she got cheated, fooled. without consent of victim her bf can marry it is not an offence.

Police will not take action against marriage of that person.

But your sister can lodge FIR against him for sexual harassment by fake promise to marry her.