Defendant filing an impleading application in partition suit

If the left out parties are willing to participate in the partition suit then they can file a petition before concerned court for getting them impleaded as necessary parties.

If they don't take any steps you can file a memo before the court stating that the other legal heirs have been intentionally omitted by plaintiff in the suit for partition, hence as necessary parties, they are to be impleaded and the plaintiff may be directed to take steps.

Each and every shareholder of property  are necessary party in suit of partition  and suiy is bad on non joinder of necessary parties and not maintainable, you may raise an objection in this regard. 

Why other siblings are left out from impleading them in the partition suit, which is bad in law ? 

What is the opinion of your lawyer on the issue ?

Thank you so much for all the replies sir.My advocate is saying suit can be dismissed because of non joinder of necessary parties or judge may order 9 shares. The other siblings were left out because plaintiff wanted to make 5 shares. Plaintiff in 2016 when the defendant advocate did a cross examination he admitted about 9 children and he admitted 1/9 th share.
As a defendant no. 7 D7 If I have any options to bring my 3 sisters on record without their signature it will be good. As a defendant Can I not submit impleading application requesting to add 3 more left out sisters and  bring them on record and issue suit summons to them? Thank you. Please suggest best possible options I do not want the case be dismissed for non joinder of parties.