(New Jersey, USA)
Trying to keep siblings involved is about as silly ass telling a deadbeat absentee father to care about his kids.
They will make token gestures from time to time but will in no way share responsibility for the elderly parent. You will just become more frustrated if you try to involve them when they couldn't care less about their elderly parent.
As far as support groups go, why would somebody take care of an elderly parent and then use their free time to talk about caregiving?
I never understood that one. Go to dance classes to keep sane and take a million 10 minute breaks to walk around the block. People, take care of yourselves as well as your elderly loved ones.