There is no right or wrong way to go about this.
It all depends on whether you would feel willing and able to take on a role as caregiver if it ever comes to that, and how likely it is that this would happen.
A lot of it also depends on his character. Some people will feel ill or weak and gladly let someone else take care of them. Others will try to maintain the balance in the relationship by doing what they can and contributing that way.
My mum was with my stepdad for 8 years, until he died. I was 9, my brother was 6 when they met. He was sick, but this was the '90's and nobody could say how long he had.
He was too sick to work, but he was wonderful. He took care of the house, cooked for us, had fresh cookies waiting when we came home from school, helped us with our homework.
And sometimes we'd also come home and he couldn't get out of bed.
For a long time, it felt like we had a good life. My mum sometimes had to take care of him, but he was there for all of us emotionally and every other way he could. He made us all feel very loved and valued.
Then when I was 16 we got some bad news. He stopped responding to treatments. He was dying. I miss him every day. So does my mum. He was the love of her life.
I know for a fact that my mum would do it all again if she could. Even being there while he was dying. It really was worth having him in our lives for those few years. But that's because he was a great man who didn't let his illness knock him down. I also know that my mum was able to choose him because she already had children and had no desire to have more. She wouldn't have risked having children with someone with a chronic illness.