According to the Hindu Succession Act, 1956, which applies to Hindus, Sikhs, Jains, and Buddhists in India, your mother has the absolute right to dispose of her self-acquired property by a will as she wishes. She does not need the consent or signature of your siblings or their children to make a valid will. However, she must make sure that the will is clear, unambiguous, and free from any undue influence or coercion. She must also sign the will in the presence of two witnesses who must also sign it.

If your mother makes a will in your favor, you will inherit all the properties from her after her death. However, you may have to face some legal consequences if your siblings or their children challenge the validity of the will in a court of law. They may claim that the will was not made by your mother voluntarily or that she was not of sound mind when she made it. They may also claim that the will was forged or tampered with or that they were not aware of its existence.

To avoid such disputes, it is advisable that your mother informs your siblings and their children about her intention to make a will in your favor and explains her reasons for doing so. She may also send them a copy of the will after making it and ask them to acknowledge it. This may reduce the chances of any litigation in the future. Alternatively, she may also consider giving you a gift deed for the properties during her lifetime, which will transfer the ownership to you immediately and irrevocably. However, a gift deed may attract stamp duty and registration charges depending on the state where the properties are located.

If it’s your mothers self acquired property then you don’t require other siblings consent at all. If not then all other siblings should consent and give their shares in relinquishment to your favour 

1.  It's not clear in your query as to whether your father died intestate (without executing WILL) or he had executed WILL.  

2.  Assuming that your father died intestate, then the property devolves to your paternal grandmother (if alive), your mother, you, brother and sister living in USA and your younger brother ( if his death was subsequent to your father's death and assuming that your younger brother was a bachelor) in 1/4 th share to each.

3.   In the above scenario, your mother can only bequeath her 1/4th share in the property through WILL to you and your mother can't name you as beneficiary for the remaining 3/4th's combined share belonging to you and your siblings.

4.   If your siblings can execute a registered Release/Relinquishment Deed in your mother's favour or in your favour and if your mother executes a WILL, for her 1/4th share in the property, naming you as the sole beneficiary,  only, then you can be the owner of house and 2 other sites.

5.   There's no need of your siblings or their children's signature, if your mother executes a WILL in your favour for her 1/4th share in the properties.

6.   Your siblings and/or their children may challenge your mother's WILL and if you counter it with facts, the properties may remain with you.

Your siblings ,their kids signature is not required on the will 

2) however post your mother demise your siblings can challenge the will 

3) best option is for mother to execute registered gift deed in your favour during g her lifetime 

For making WILL in respect of her mother your mother donot require any permission or consent or sign of anybody.

- If the said property was in the name of father , then after his demise intestate his property would be devolved upon all his legal heirs equally including mother. 

- Further , after demise of any of the legal heirs , his share in the property can be claimed by his /her legal heirs equally. 

- Hence, your mother can write a Will for her share in the property , and for transfiguring others share NOC/released deed required in the name of mother. 

- -However, if your father had left any Will in the name of your mother , then she has her right to transfer the property in your name by way of Will, and none has right to claim over the said Will. 

If the said properties were transferred to your mother's name by a registered document by your father to her during his lifetime then your mother becomes an absolute owner of the entire properties.

She can transfer the same to your name either by bequeathing them to your name by Will or she can execute a registered settlement deed with life interest to her.

In either of the situation a doctor certificate stating that she was sane and enjoying a good mental health and that she knew what was written in the documents would substantiate the authenticity of the said documents so that any dispute in future in this regard can be challenged properly.

No legal consequences. But your mother inherited property from husband intestate. In this manner, your siblings have 1/2 share i.e. all 4 have 1/4th share each.

Who expired first ? brother or father ?

Your mother can share her 1/4th share to you. 

But since your siblings are in USA, it will hard for them to fight court case to claim their share. So let your mother WILL all the property to you. 

 does it require my siblings and their kids who are 18+( all are USA citizens) to sign - NO

As the properties were transferred in your mother's name after your father's death 25 years before, she can very well write a Will in your name bequeathing them to you exclusively. No other legal heir can make any valid claim. No legal action by any other heir shall have any merit whatsoever.

Dear Client
In India, property inheritance and wills are primarily governed by the Indian Succession Act, 1925, and property laws specific to the state in which the property is located. Here are some key points to consider:

Writing a Will: Your mother has the legal right to write a will and specify how her property should be distributed after her passing. She can choose to leave her property to you or any other beneficiary she wishes.

Validity of the Will: To ensure the validity of the will, it should typically be executed in accordance with the law. It's advisable for your mother to consult with a lawyer to draft and execute the will properly. The will should clearly state her intentions, and it may not necessarily require your siblings to sign it.

Challenging a Will: While your mother has the right to decide how to distribute her property, there is always the possibility that your siblings could challenge the will in court if they believe it was executed under duress, fraud, or other illegal circumstances. However, the burden of proof typically falls on the challenging party.

Rights of Foreign Citizens: Your siblings, as U.S. citizens, can inherit property in India. However, they should be aware of Indian laws regarding property ownership by foreign citizens. It's important to consult with an Indian lawyer who can provide advice on the legal requirements and implications for foreign citizens inheriting Indian property.

Legal Consultation: To navigate this situation successfully, it is strongly recommended that you and your mother consult with a qualified Indian lawyer who specializes in property law and succession planning. They can provide guidance on drafting the will, the legal requirements for its validity, and steps to minimize the risk of legal challenges.

Tax Implications: Inheritance tax laws in India may also apply, so it's important to consult with a tax expert to understand any tax obligations associated with inheriting property.

Hello , in your case ,

yes your mother can do will on your name but after will and after the death of your mother if you want to sale the any of property which you received by will you must have to go for apply probate application in the court to sale that property.

second thing, ones your mother do will in your name. no other sibling having a rights on that property. on otherhand any of the sibling's want to create any dispute, they can only challenge that will on civil base case.

and no any sibling's signature require while doing will.