Badders, I completely understand. My dad became ill about 8 years ago when DC were 11 and 13, and both transferring to secondary. I was working full time and running a small business. Luckily DH's work does not involve too much travel, and he did more than his share of housework, but we were barely coping.
We had a couple of summers where each weekend we seemed to crisscross the country dropping kids with grandparents, at sports camps and so on. At one point we packed a 12 year old on a Euro Star on her own (to be met at the other end!). And a 14 year old, without a word of German, on a flight to Hamburg. The same 14 year old managed found his own way back from Cirencester, armed with taxi money, coach ticket and tube pass.
I hung on for the first three years, then voluntary redundancy was offered across the organisation I worked for. I realised I would probably not get another chance and that my mum was on the brink of needing a lot more help.
It was in many ways a perfect job for me, and I was good at it.
I find it difficult when my mother complains about how I don't do anything for her. It is the dementia talking, but I face another decade of caring for her. My in laws are now getting to the stage where they may need help, but are not looking ahead. (I understand the denial, as looking ahead would be grim, but I dread us having to go in and pick up the pieces again.)
It probably did DC no harm to realise they were not the sole centre of their parents universe. But I wish I had not been so tired through key teenage years and could have enjoyed them more. In my mother's case, caring is complicated by the fact most of her assets are in property. I accept it provides a useful income, but resent the fact I had to spend a month of my daughter's last summer at home, 150 miles away, trying to bring her old home up to an acceptable rental standard. (And she still complained each time I saw her, that I did nothing.)
When I gave up work I also found I needed to rebuild social networks. Old NCT friends, say, were used to meeting up without me, and I needed to take the initiative in organising things with them. I was also very tired, and spent a lot of time in the first six months doing nothing more than watching day time TV. In retrospect I probably needed it but I worried at the time. I was supposed to be doing so many other things.
It's OK, we have found a few silver linings in having to spend part of our lives near my mum, and I could not have carried on. And things are much easier now both DC have left school. But I still struggle with the fact that my life is hold.