Property dispute among three brothers

(i) We (three brothers say X, Y, Z) purchased a plot, got registered in our name in Ghaziabad without disclosing ratio of ownership. Land cost is borne by only X, Y and joint Housing Loan among all three (X, Y, Z). (ii) Dispute is with X, Y with one party Z. (iii) One written agreement signed among three parties which neither registered nor notarized. X and Y paid Rs. 7 lakh to Z in writing through agreement for construction of 2nd floor. As per agreement, each one is living in one separate floor (03 floor ; ground, 1st and 2nd floor - Z on 2nd floor). The ground and 1st floor were constructed by X and Y and in their possession. Z did not pay loan installments. Loan was defaulted and ultimately X and Y paid whole amount. (iv) Z filed civil suit for declaration for 2nd floor which he lost. (v) Now, X and Y are interested in evicting him i.e., land / property would be in name of two only X and Y by deleting name of Z. Under which law, such civil suit could be filed.