Where did the money come from that was put into your separate accounts and then used to pay the mortgages? If the answer is each of your earnings during the marriage, then the fact that the payments were made from separate accounts isn't particularly relevant.
That said, given the very short duration of your marriage, and assuming no other significant marital or non-marital assets or debts, I would be hard pressed to believe you wouldn't settle the property division by basically taking away from the marriage what you brought into it.
Anyone can "go after" anything. That your brother hasn't paid anything on the mortgage isn't relevant to what might happen in a divorce between him and his wife (I assume your reference to "her wife" was a typo). You might want to talk with your brother about having him deed his interest over to you.

