I understand your pain in this, went through it as a medic with some patients, and with family too.
As much as it breaks your heart, you have to keep them in mind. Yes you will lose it, we all do with family, but the one thing to remember is they are probably a bit scared too. This is uncharted territory, a step into eternity to put it mildly. You are extremely important to them and will be the last person they see here.
With my patients, i looked at it as an honor wierdly enough to hold their hand as they passed. Yes, i would tear up a bit, but this was where i was supposed to be at the time. Usually i had no idea who they were, just that they wore a uniform.
When it was my family, i would have a tear - doing everything i could *not* to breakdown. I would place my hand on them for physical touch (for myself and them) and let them know what they meant to me and how much i love them.
-im welling up a little thinking about the last tine as i write this.
My heart goes out to you, your family and your aunt.