This is a pretty big "ouch", since paizo ruled that bloodragers bloodlines can be advanced by dragon disciple levels and their bonus feats lists are slightly different. The relevant text for this is the following:
Upon reaching 2nd level, and every three levels thereafter, a dragon disciple receives one bonus feat, chosen from the draconic bloodline's bonus feat list.
This is what I would propose:
If you have levels in sorcerer, you get the bonus feats from the sorcerer bloodline. If you have levels in bloodrager, you get the bonus feats from their list. If you have levels in both - well, this doesn't even work without putting the dragon disciple into the equation and would require a decent amount of time to make it work, so I'd skip that for now and default to the sorcerer bonus feat list.