Hi
The land had 3 heires after your dad death.
If there was a written release or relinquishment deed in your both name by mother , the right is equal for both brothers.
If not any written document your brother can not sell the land as long as it is undivided and need to get either NOC from you and mother,
Or an order from court.
You can make a public notice disclaiming the responsibility and refraining from the buyers.
At the end your brother had a right in the father's property so he can get it sold through a court order after seeking partition in court.
The another legal step is thatc am taken by
Your brother's wife and children can stop him by getting an injunction not to alternate/dispose the property ,
from court by filling a domestic violence case on grounds that they need a shelter and maintenance.