Civil suit

If the other defendants don't file vakalatnama or appear before court as a party in person then they will be set exparte and the orders may be passed in their absence which may be even against them.

Yes it's mandatory to file vakalatnama to represent your case other wise case will be decided against you, yes you can ask Lawyer of defendent who file vakalathnama to include all you 7  names.

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I am of the view that in a suit filed by multi persons as a party to the suit, Vakalatnama can be signed by one of them and not necesarily by all of them including Affidavit. However, each person should file their respective Affidavit for other purpose in the suit, and this is the same in a writ petition.