You can backup your messaging history using Helium (Carbon) or SMS Backup and Restore. When you use Helium to backup 'messaging' it also will backup call history, only bad part is it won't restore MMS/SMS pictures. Or at least, it pics won't work with the default Android Messaging app or Hangouts. SMS Backup and Restore will. SMS Backup and Restore also does a great job of cleaning up dupicates and the backup it produces is a human readable XML file. If you are a programmer, you can do many things with XML such as db queries or open just opening it using internet explorer or even importing into Excel. That could help you bulk filter/save your messages with your brother.