I am a caregiver of a younger sibling who has cognitive impairment and will be tested to Alzheimer's. Are there any support groups out there for me?

Even though you are a sibling and not a spouse, www.wellspouse.org may be of some help. I hope aging care can help, too, as many people here have spouses with early Alzheimer's.

Please, also, try www.alz.org or call your local Alzheimer's association. They can be very helpful. They have a 24/7 helpling and support meetings.
Take care of yourself, too.
Carol