I lost my favorite aunt three years ago. She was my mom's twin sister and virtually my second mother. She took care of us as children when my mother was going through multiple surgeries for a back problem and then later when she had trouble getting off the meds.
My aunt "Twin" (both her and my mother had that nickname) was 55 when she passed. She had a heart attack while she was sleeping and stayed on life-support for several days before they decided to pull the plug. It was VERY hard for me to take her death because it was unexpected and my wife was less than two months away from having our first child delivered. I lived out of state and when my aunt talked to me on the phone, all she could talk about was seeing "that little baby girl". She frequently said that she couldn't believe I was finally going to be a dad. (I got married in my early thirties, which is LATE by the standards of my hometown.)
The day of her funeral, someone (I still don't know who) put me on the pallbearer list. I did not want to do it, but I went through with it anyway. I think it may have helped me accept her death in some small way and I'm glad now that I went through with it.
I still feel like something is missing every now and then. Especially when I need to talk to someone or have good news to share. It feels like I'd imagine a person who's lost their pinky-finger must occasionally feel. I never knew she was so important and how much I depended on her until she was taken away.
Acceptance is a long journey, but you and your family will make it, in time. I pray that you and yours will find peace in each other while you're coming to terms with all of this. I understand how you're feeling and I wouldn't wish it on anyone. God bless.