My legal right for my land in family.

my dad owned 10 acres of farm land and i have a elder brother and one married sister, my dad passed away 10yrs ago and we both the brothers decided to divide the property and was accordingly impliedly agreed between us and he was given 5 acres of total land and he eventually sold his share of land over the years and i confirmed on all those documents , and now he has an eye on my 5 acres of land and recently he published a paper notice that the balance 5 acre land which i hold in my name and has 7/12 on my individual name is a family property and he also has rights on my piece of land and claiming right on the same, what legal remedy i should take??