Hi.. Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concerns.. As per your complain it seems that your brother is having Chronic Sinusitis and mucous formation which discharge through nose and post nasal drip is commonly seen in sinusitis.. Bad breath and foul smell from mouth and nose is also due to sinusitis.. I would suggest you to consult an Otolaryngologist and get evaluated and for sinusitis initially antibiotics like Augmentin or Azithromycin can be advises. Anti-inflammatory painkiller like Ibuprofen can be given. Decongestants like Pseudoephadrine [sudafed] and mucolytics like Ambroxol can be give. Steam inhalations and saline nasal sprays will ease in draining mucous easily.. Use a humidifier in his room.. In case if still there seems no relief further investigations like PNS view X-RAY or MRI of salivary glands will be done to rule out for other conditions like Polyp in the sinus. If medical treatment does not work then surgery can be planned to drain the sinuses or removal of pathology like polyp.. Hope this information helps.. Thanks and regards. Dr.Honey Nandwani Arora.