The helpline isn`t open until tomorrow morning but please phone the Samaritans. They have an emotional listening service and might be able to help you.
hi @Shellb
it can't be easy for you and your sister with your own young families and both working, and your parents so young themselves
if it helps, write out here anything that's on your mind
if you want to chat in real time, maybe call the Helpline tomorrow https://www.alzheimers.org.uk/get-support/national-dementia-helpline