Yes they can join the same only if they have rights for the same or owner's authorise them

1. only the rightful owner of the property can enter into a valid and binding agreement for development or sale of the property. In the present case, Mr. A is the rightful owner of the property.

2. minors cannot enter into a valid and binding agreement and hence the agreement executed by them shall be voidable at the option of the minors.

3. only the consent of Mr. A and his two daughters is necessary for a valid and binding agreement to be made..

A is absolute owner of property 

consent of his children ie sons and daughters is not necessary to execute development agreement 

they cannot give title to builder when they don’t have share in property 

You are buying the property either from the builder or from the landowner out of his share.

The JDA made between the developer and the parties to the agreement is not your concern. 

You may obtain a legal opinion from an experienced lawyer in the local and proceed with the purchase if recommended. 

Since the property absolutely belongs to 'A', there was no need for the son-Mr. B to have executed Release Deed as also daughters C and D to have executed JDA. Nevertheless it would be an added point for the prospective buyer of the property.

if property belongs to or is owned by A, then there is no question at all of his children being signatories to the JDA

Son B has no right share title or interest in the property. So what was he releasing ?? he only has a future right in the property as a presumptive legal heir of his father, provided that during the lifetime of the father, the father has not dealt with his property, say by selling it or making a Will for it

son and daughters and the minor children of the daughters are not at all required to be parties in the JDA

You can proceed with purchase of flat 

Get documents vetted by local lawyer 

You were advised to obtain a legal opinion from an experienced lawyer and proceed only if recommended. 

Get the property papers vetted by a Lawyer and based on his opinion, take decision as to proceed further or not. 

You first check the title of the said property and whether it has any emcrumbrance 

I'm sorry to hear about the difficult situation you are facing. As an AI language model, I am not authorized to give legal advice, nor can I determine what legal actions you should take. However, I can provide you with some general information and guidance that may be helpful.

It is advisable to seek legal advice from a qualified lawyer who specializes in family law, as they can help you assess your legal options based on the specific circumstances of your case. They can also help you understand the various criminal charges that may be applicable in your situation and guide you through the process of filing such cases.

Based on the information provided, it appears that your wife has engaged in several wrongful and deceitful actions, such as forcing you to buy a flat, threatening you, trying to sell the property without your consent, and making false claims for income tax refunds. These actions may constitute offenses such as fraud, cheating, criminal breach of trust, and forgery, among others.

However, to establish the criminal liability of your wife, it is important to gather strong evidence, such as documents, emails, or recordings, that can support your claims. Your lawyer can help you gather and present such evidence in court.

In addition, it is crucial to remain calm and composed throughout the legal proceedings, as any aggressive or uncooperative behavior can harm your case. It is also advisable to avoid any direct communication or confrontation with your wife and follow the legal process to seek justice.

I hope this information is helpful, and I wish you the best of luck in resolving your situation.