1. Every sharer is required to get one fifth share in the property it is ancestral as there are fours sons and FIL.
2. Any sharer who gets less than one fifth can seek proper division of property by filing a suit for equal share of property.
3. The suit can be filed in district Court.
4. Husband need not visit India for filing such suit. It can be done through a GPA given to any of his well wisher.

I presume Deed of settlement is duly stamped and registered 

2) it is binding on all family members 

3) you have to file suit for partition to claim your one fourth share in the property 

If the transfer of property among his sons was made by your father by executing a registered settlement deed then it is valid and cannot be cancelled or altered suiting any individual's convenience or selfish motives.

Your husband can file a suit for partition and claim his share in the property as per the registered settlement deed.

Now when the entire property is disputed in the partition suit the other brothers will become scared of losing their share in the property hence there are possibilities for an amicable settlement among everyone, therefore the solution for now is to approach court with a civil suit.

- If the said property is self acquired property of your father-in-law , then he has his legal right to change and give the said property to anyone without taking consent of any of the legal heirs. 

- However, if the said Settlement deed is registered from the office of Registrar , then he cannot change the same without a court order. 

Your husband legally owns 1/4th share as per the settlement deed, and his brothers cannot reduce or alter it.

1. 
   Deed Cannot Be Changed – If registered, modifications require your husband’s consent.
2. 
   Equal Share Right – He must get his full 1/4th portion, not a reduced share.
3. 
   Legal Action – He can issue a legal notice or file a partition suit to enforce his rights.
4. 
   Sister’s Share – Any share given to her must come from the others, not your husband's portion.

Act fast to secure his rights. Let me know if you need a legal notice draft.

For detailed, personalized advice, consider a phone consultancy. Hope you find the information helpful. You are free to contact me for further discussion. If you could spare two minutes of your time to write a review, it would be greatly appreciated and bring immense happiness to read it. Thank you. Shubham Goyal.

If the deed is genuine then as per the deed the each signatory will get their respective share.

Such share can be further altered only with mutual consent of all stake holders. 

No they cant change the same you can take legal action against them

Madam,

Your husband do have equal rights as that of his other brothers/siblings. You may get an special power of attorney from your husband and agitate his rights yourself.  

Your husband has strong legal rights in this situation, as per the original settlement deed executed by his father 18 years ago. Here’s what you need to know:

1. Rights Under the Settlement Deed

• If the deed clearly grants 1/4th share of the property to your husband, no one can alter or reduce his sharewithout his written consent.
• The fact that the family unilaterally divided the property and reduced his share without his consent is legally invalid.

2. Can the Settlement Deed Be Changed?

• 
  No, once a registered settlement deed is executed, it cannot be revoked or modified unless:

  • Your husband voluntarily signs a relinquishment or gift deed.
  • A court declares it invalid due to fraud or coercion.

• If the family has given additional land to the sister, they cannot take it from your husband’s share unless he agrees to it legally.

3. What Legal Action Can Your Husband Take?

• 
  Demand Partition & Possession:

  • Your husband can send a legal notice demanding his rightful 1/4th share as per the deed.
  • If they refuse, he can file a partition suit in court to claim his land.

• 
  Challenge Any Illegal Modifications:

  • If his share has been reduced without his consent, he can file a suit for declaration and injunction to prevent any further construction or sale.

• 
  Injunction Against Construction:

  • If they are building on his share without his consent, he can seek a stay order from the court to stop it.

4. Immediate Steps to Take

• Get a certified copy of the settlement deed from the sub-registrar’s office.
• 
  Issue a legal notice through a lawyer demanding the correct share.
• If the family does not comply, file a partition suit in court.

Since your husband is overseas, he can give a Power of Attorney (PoA) to a trusted person or lawyer in India to handle this matter legally. Would you like help with drafting a legal notice?