Apple Watch ultra

That's really nice of your brother. Ask him to give you money so you can purchase an Apple Watch Ultra in India. The Cellular bands of Apple Watches sold in the US are specifically set to carriers in the US, Canada, Mexico and Puerto Rico. While it's possible you may be able to get a carrier in India to be able to support a watch purchased in the US, it's more likely they won't. And your watch if purchased in the US will have absolutely NO warranty in India.

Buy the watch in India and let your brothers money not go to waste on something which may not work as you hoped.

Good day to you ashmeet163,

An Apple Watch will power on and pair to an iPhone that meets the system requirements anywhere. However, it may not be compatible with cellular networks or have all capabilities in your region. 

Here is a link that goes over which models are compatible with which carriers. Apple Watch - Carriers

Here is a link that goes over watchOS Feature Availability - watchOS - Feature Availability - Apple

Thanks. 

You're welcome. Glad to help.