Since Mom died I feel like my whole family is falling apart and I don't know how or if I can fix it

My Mom passed away last July, literally 364 days after my beloved grandmother, then my stepmother on Sept 15. Since then so much has changed, my head understands but my heart is broken. Though Mom and I didn't always have the best relationship, I knew she loved me and only wanted the best for her children, even thought at times I didn't feel loved, and felt that she chose the men in her life over me and the boys.
I have a brother, 2 half brothers, a half sisiter and 2 stepsisters and a stepbrother who I love dearly. Unfortunately my brother, stepbrother and one of my stepsisters live away so we don't see each other often. Though I admit since Mom died, my brother and I have kept in regular communication....we all seem to be having a hard time and can't seem to talk about it to one another. Its almost a forbidden topic.
My stepdad who really is my Dad, has Parkinson's and Lewy Body Dementia. That has been hard enough, we knew things would get difficult as the disease progressed. He had a mini stroke in early Feb which accelerated his dementia and is now in a small special care home. He seems to like it there, and so for that I am grateful.
I have been off on stress leave from work since the end of Jan and have seen a therapist once so far, but still having a hard time putting my grief in the right place.
On top of all that, one of my half brothers has been in and out of prison for minor theft and drug charges, he is 16 years younger than me and I have been more a mother than a sister to him. He got out of jail the first time 3 days before Nanny took her stroke so was home for her funeral. He got out 4 days before Mom died. 
I know he felt jinxed, but I tried to tell him it was a blessing because it would have been worse having to attend your mothers funeral in shackles.
On Thurs, he was sent back to prison for 2 years for theft to feed his addiction, I had it out with him before Christmas and said some pretty severe things to him, but I felt it needed to be said....Mom would be so very disappointed in him, among other things. I don't regret what i said, Mom sheltered him so much and he has told so so many lies....even to himself.
My girls are both good kids who I have never had to speak to them like that, they have never caused me problems, and are not into partying or drugs. 
I don't know why I feel so bad, I just feel like Mom would want me to take care of him, but I am at the end of my rope, and I am still really not dealing with my grief over losing Mom.