Yes, a law firm representing a creditor and presumed plaintiff with respect to your question can continue to have you served with the presumed summons and complaint with respect to the matter against your brother even though he has a presumed written agreement resolving the dispute.I suggest that he contact the judgment creditor and ask that the process server be called off with respect to his debt followed up by a confirming letter by him where he keeps a copy of it for future reference and need.It is imperative that he have a signed installment agreement by the judgment creditor regarding the debt that you are writing about.