how to join, interested person, as defendant

plaintiff filed a suit for injection against dipendent who is his close friend.
plaintiff has mother and 3 brothers, plaintiff father was died ,.
plaintif created a forgery will in favour of him. intentionally he filed injection suit against his friend to get order in favour of him. he didn't add his mother and brothers as defendent.

how to add them as defendent in cpc
Order 1 , Rule 10 or Order 1 Rule 8 ?
please answer