For gift deed in favour of brother attracts 3 per cent stamp duty 

from sister in law it would attract 5 percent stamp duty 

It attracts nominal stamp duty of Rs 200 

Stamp duty is not based on mutual relationship between the donors. 

It is on the conveyance that parties enter into. stamp duty of the state in which the property lies, is required to be paid.  

Its not clear as to which state your query is related to. 

In India stamp duty for registered deed is not universal. 

Therefore mention your state. In WB it is .5%.

it depends as per state law. Every state has its own rates. Kindly check with the state in which you have property.

In general it is same for sale

It's as of bow is 3% and for husband and wife it's nil just registration charges it release deed or quit claim deed.

Stamp Duty in Pune

1. 
   Gift Deed in favor of Near Relatives (in favor of Husband, Wife, Son, Daughter, Grandson, Granddaughter or Wife of a deceased son) – Rs. 500/- Stamp Duty, and Rs. 200/- Registration Fees (1% LBT is exempted till 31 December 2020).
2. 
   Gift Deed in favor of other Family Members (not in favor of near relatives) – 3% Stamp Duty and 1% Registration Fees (Max Rs. 30,000/-) is applicable (1% LBT is exempted till 31 December 2020).
3. 
   Gift Deed in favor of other than Near Relatives and Family Members – Equivalent to Sale Deed/Conveyance Deed.

It depends on the state to state scenario. In Maharashtra it's lowest for blood relatives

If this property is situated in Maharashtra, then there is no stamp duty payable for transfer of immovable property within blood relations. 

according to Article 34 of the Maharashtra Stamp Act, which was amended in 2017, stamp duty on gift deeds is 3% of the property's value. However, if the property in consideration is a residential or agricultural property and is gifted (without any payment) to family members, then, the stamp duty is Rs 200.

According to Article 34 of the Maharashtra Stamp Act, which was amended in 2017, stamp duty on gift deeds is 3% of the property's value. However, if the property in consideration is a residential or agricultural property and is gifted (without any payment) to family members, then, the stamp duty is Rs 200.

A gift deed is the preferred option instead of the partition  clause under Article 46 of the act where the stamp duty remains the same at Rs 200, but permission of all the family members is required.

3%

stamp duty is state subject varies from state to state. 

around 3% of the property value has to be paid as stamp duty in case the property is being transferred in the name of spouse. 

- Yes, they can transfer their respective property in the name of younger brother after executing a registered Gift deed 

- Further , as all the three are blood related , then the stamp duty is 2 percent .