No builder cannot do so it is criminal offence it is cheating fraud and breach of trust and if he did so by forged documents he need to be prosecuted for same and the transaction has to be cancelled by way of filing a suit .

1) If the property is registered on your father-in-law name than need to check all mutation papers from last 30 years till current date.

2) If your land area has been under the control of land mafia than the above situation may take place.

3) So without look or reviewing the land papers it's hard to come on conclusion what went wrong exactly. 

4) Kindly provide Name, Survey or Katha Number and other agreements, address of the property.

You cannot be forced to sell property  against  your wishes 

2) builder cannot  sell property to third party once property is registered in your names 

3) in case builder has done so file suit to set aside subsequent sale deed 

4) file complaint of cheating against the builder under section 420 of IPC 

See entry in the EC may be wrongly or fraudulently made seek the complete information and then initiate legal action on same.

Take search in sub registrar office whether any sale deed has been registered in another party name 

No it's a illegal act of cheating. You can file FIR, you can file suit as well as Consumer dispute in this case

The land was purchased by you and a registered sale deed was done. But the mutation must also be done in the revenue records. If it is not done the name of the previous owner shall reflect in the records. Your sister must have done the mutation as the property was registered in her name.

In your case it was through a power of attorney and the supreme court has held that selling or buying through power of attorney does not confer ownership rights.

Regards 

Yes it may be possible and therefore you should come and get it registered in your name and change in the records.

Normally any transaction which is registered will get reflected in the Encumbrance Certificate (E.C). At times there might be missing entry in the EC. This can be stated to the concern Sub-registrar and he will issue a fresh corrected E.C. Get it scrutinized by a good property lawyer in your locality, for satisfaction you can obtain certified copies from SRO. 

1. Check whether the dale deed you have properly registered or not.

2. if both your husband and your SIL jointly the same land then EC shows either of their name which is alright.

3. If you were the first buyer then subsequent sale by the developer of the same land to someone else is not harming to your title.

4 Visit the Revenue office and check the records to find out any anomaly.

5. if any mischief is there then better sell it and in vestment the money in some other clean property. 

1. firstly your FIL needs to check with the authority how the EC is reflecting someone else's name when property stands in your husband's name

2. plz ask him to apply for a certified copy of the agreement under which the person whose name reflects in the EC has been sold the property

3. secondly check the POA whether it has a clause for power to sell on behalf of owner

4. if there is any such clause then the POA is compulsorily required to be registered, check that

5. you need to investigate as to how the EC is reflecting a third party's name and accordingly take necessary legal steps to delete that person's name by filing a suit in court

Any immovable property which is registered in your name cannot be sold by the builder without power of attorney which should be registered in his name authorising him to do the same.

If the same has been done by the builder you can file a police complaint against him for cheating, fraud, criminal breach of trust and forgery under section 406, 415, 420 and 468 of the Indian penal code.

Before proceeding to file the police complaint please check thoroughly with the registrar office whether the same is a typographical error or fraud has been played by the builder in reality.

Can be sold but it`s a criminal offense, Actual ownership will rest in you. Can file police complain against the builder.

Anything possible, builders and govt. employees are crooks.

Dear Sir,

Lodge FIR against that builder Or file criminal complaint case by alleging fraud before.magistrate....you can also file civil suit for declaring sale deed of third person and purchaser null and void... 

You will have to file a civil suit for declaration of title against the person who sold the property and who purchased the property with an additional relief of declaring the sale deed in favour of third person as null and void. 
You have a strong case.

1. Did your father in law executed a POA in favour of the builder while executing the development agreement with the builder?

2. If yes, then he might have misused it and soild the land to some one with out youyr knowledge.

3. First of all conduct a search from the local office of your Registrar and collect certified copy of the deed of conveyance registered therein in case the said prioperty has been found to be sold.

4. Thereafter file a declaratory suit praying for a declaration that the said sale deed has been fraudulently registered without your knowledge and consent making it invalid and also praying for a direction upon the Registrar to cancel the registration of the said Sale Deed. 

It is not possible for someone to sell the property to a third person without any valid documents or without any title to the property until and unless the seller used fraudulent means to sell the property by creating fabricated documents and impersonate the original owner before the registrar's office.

Your father in law might have mistaken the EC hence you may better obtain the certified cop[y of the document which is showing the transaction in the EC on a third persons;'s name and decide about the legal course of action to protect your interests in it. Discuss with your advocate at length on this and proceed.

Have you sen the details and scrutinized the same properly before jumping into any such conclusion?

You may consult an advocate in the local and then decide about next course of action on this.