Can we challenge on order of partition suit in higher court

Hi all one of my client who is working in pvt company, he having 2 acres of land and he was staying with his grandparents but they take care of him as a own son (kind of adopted) but they dont have any legal paper (" Adopted") but whole society known he is only son of the That grandparents, and his grandparents having 4 daughters viz mothers sister of my client. they filed suit against my client (partition Suit) and got preliminarily decree as a share of the 1/5th, my query is : 1) the defendent is very stranger from the suit. 2) he dosnot know what they have did with his and 3) once he was got notice from the court then they said nothing to worry, you just keep calm. 4) finally after 25 years they mentioned in plaintifs suit he is not a legal Son or Not a adopted son, just my parents are helped him when he was a child and no more of his parents. Now can we go to higher court for the challenging of this Sr Div order. please sugges us. Thanks in Advance.