Unfortunately, there probably isn't going to be a way to fix this for console. If console allows the command (it may or may not), and you can get admin status (not sure if you can), you could try doing a chunk reset or region reset command (cr and rr, respectively... use cr help or rr help to see options for using those commands) to reset the area where you are and maybe it will fix that area so your brother can load into the game again. It isn't a guarantee, and I have no idea if you even have these options available on console. But it's probably the only chance you have to fix it on consoles.
From what I've been seeing, it seems like consoles get less stable after around 100 days. You may want to consider limiting your games to under 100 days to help reduce the chances of corruption. I know that isn't what you want to hear, but until TFP can figure out what is causing people to have trouble on consoles after 100 days, it might be the only option to avoid this happening. That, or just play as long as you can and if the save breaks, then start over. If you're planning to start over when it breaks, then it breaking isn't really a big deal anymore.
You could maybe also increase the frequency of the automatic chunk resets in your game options as that may help to keep the game's save files from getting too large. It's possible that because consoles have only a limited space that they allow for saves, that your saves are getting too large after 100 days and that's preventing them from being allowed to properly save, causing corruption.
Last, there is a known issue with lag/stuttering in 2.5 and that has the potential to corrupt a save. I'm sure TFP is working on fixing that, so that may also help prevent this problem once that is fixed. Of course, none of that helps with your currently corrupted save.