I think that some of the posters here have made some horrible comments. It easy to say well stop caring for your parents. Then the comment well go PT in your job when some has 4 teenaged kids who always need food, shoes, clothes and money is not helping either.
I know a lot of people at the moment with parents aged from their 70's to early 90's.
I know elderly parents who stepped in with financial help when their kids were buying or building homes. I also knew grandparents who helped out a lot or minded grandkids so both parents could work. Other parents then though about the future and made plans for this.
If your parents live a distance away from you they need to accept that careers and cleaners will be coming into their home. I say to your parents that your looking into getting them more help so they can stay in their own home for as long as possible. Contact social services and their local GP to see what is available and apply for this. Apply for the attendance allowance as well and use this money to pay for more cleaners and careers.
When looking after elderly parents it's a sprint and not a race. You need to delegate as much as possible and be willing to pay for this. If your parents have some money say to them it time to spend to make life as comfortable and easy as possible.
I would contact your brother and met with him face to face. Tell him that your no longer willing to keep doing everything for your parents and you need him to do more. Tell him he needs to visit them twice during the week and bring them to every 2nd medical appointment.
Tell him that your tired and your family need you as well and that unless you start getting a break you end up sick and it will all fall on his shoulders. I would say to him as well the longer your parents stay at home the better because otherwise what they have will go on care home fees. If your brother wants an inheritance down the line this might help in making him step up a bit.
The reality is that if you keep going at your current pace your going to end up either sick or in bad health yourself. You need to delegate stuff at home as well to your kids liking washing and cooking dinners. You need to spend time with your kid's and see how school and friendships are going. They need you when it comes to exams, UCAS forms ect for support and guidance.
If your parents object to extra help well just say I can't come here as much and I am trying to let you live at home for as long possible. I say as well that I have 4 teenagers at home and it coming to exam time ect. Your not been mean to your parents but your letting them know the reality. I get a Samsung 10 inch tablet and internet in the house for them as well so you and the kids can face time then. Arrange an online shop and get it delivered every week with milk, bread ect.
Get a cleaner in twice a week say on a Tuesday and Friday and get them to remove and wash bed linen and clothes one day and hang them up to dry. Then on the 2nd they sort out, iron and put away things.
Let your visit to your parents be one to sit down, have tea and chat rather than trying to do everything in there house also.