Ownership Of Land

My mother's father (grandfather) purchased the home from his elder brother without any note 40 years back. And my grandfather gave some land to my mother without any documents 22 years back. We are paying taxes for the land from the very beginning and we constructed a home last year on that land with permission from the village authority only. Now my mother's cousin is telling me that the property is in his father (my grandfather brother) name(But we don't know it is sure or not). What should I do legally to make it as on my mother's name?