He was a real SOB. Henry was right to be mad at him for not telling him she was sick. Of course he didn't spend enough time with her in the end to actually know she was sick.
I was leaving actual history out when I said Margaret the sister in the show died of Consumption. I'm positive that is what Brandon told Henry. There was the episode where England was plagued with the Sweat, but that was a bit ealier in season 1.