This could be from the Chronicles of the Kencyrath by P.C. Hodgell. Jame and Torisen are Highborn twins (sister and brother respectively) of the Knorth clan, although various circumstances of their world and upbringing have resulted in significant diversion, including in age. The Highborn are able to bind others to them by blood, and Jame's blood is particularly powerful, with one of the conflicts in later books being that Jame's blood overrides Torisen's control, not a great thing since he's also their Highlord leader. Torisen does have scarred hands, both due to an incident in his past where he was tortured by religious fanatics who bound red-hot wires around his hands and later injuries due to him wielding the traditional Knorth family sword, Kin-Slayer, which was broken in the past, resulting in a jagged handle.
Torisen is not the "angel of death", but he is one of the avatars of the three faces of his race's god, specifically that of Preservation, with Jame being the avatar of Destruction. It's a bit unclear as to what the result of the three faces of their god manifesting will be, but the implication is that it will involve breaking the world apart and then putting it back together in an improved form.