Can brother register his property to an unmarried sister?

Yes you can do it.

Yes, if you are absolute owner of property then you can transfer it to your unmarried sister but  after being transferred the property to your sister ,you will have no concern with property and can't insist/Pressurize your sister for re transfer the same to you, it will depend on her.

Noted. Thank you very much sir

you can either gift or sell the property to your sister; The court fee applicable as per document of Gift or sale deed; but then your sister will be owner and she will be at her will to return gift back or sell you back, 

Becareful while it may not even starn relatiosnhip as most of such cases came where people cheat

Whether it is your self acquired or ancestral property ?

What (which document such as sale, gift etc.) do you want to execute and register ? 

Dear Vashista Sir

i am purchasing a agricultural land from another owner. Since, the Owner is insisting to register within this month and as I am now currently residing in abroad, I am planning to get the property registered to my unmarried sister and to get the gift settlement from my sister to my name in March 2023 when I will be in India. This is my plan. Whether there will be legal issue on this?

No legal issue ,only belief and trust only .if both have good relationship then queit o.k.

Noted. Thank you very much Sir

yes any brother ragister him property to his sister when he is owner of property . any peson sale our propety other  person 

You have stated, inter alia, that, ".....I am planning to get the property registered to my unmarried sister and to get the gift settlement from my sister to my name in March 2023......." which implies three different statements viz;

1. Regsiteration of property being purchased in the name of your sister,

2. Settlement of gift from your sister

and

3. From your sister to your name 
please be clear as to what is planned qua registration of property under purchase. 

Noted. Thank you very much Sir

I would like to register a land to my unmarried sister
 

CERTAINLY LEGAL YOU CAN BUY PROPERTY FOR YOUR SISTR

can I re-register that land from my sister to my name or not?

CERAINLY NOT UNLSS YOUR SISTER (LEAST EXPECTED) IS CHARITABLE TO YOU. SHE IS THE ABSOLUTE OWNER .

SO DONATE PROPERTY TO HER WITHOUT ANY HOPE OF GETTING BACK.

It may sound hard to you (unpleasant also) You are not going to be 1st or last NRI to be fleeced by siBlings.

Is there any legal disputes on this?

NOT AT THIS STAGE.

LAW (FULLY AGAINST YOU) WILL BE SHOWN WHEN YOU WANT THE PROPERTY BACK.