to sum up, all your character progress is saved under your player cloud id which is seperate from your brother's player cloud id. but once you buy your own game again you will have access to what progress you have on your account for the base game, then when the dlc's come back as you buy them you'll have access to the characters where you left them. Again your account is connected to dbd seperately than your brothers but your steam has to acknowledge your dlcs once your steam starts keeping track of things. also I think your achievements will be the same :)