Are adult children morally obligated to care for aging parents?

My parents were what I consider pretty good parents. My dad was an alcholic. He said and did some nasty things like drive drunk on a regular basis with his kids in the car, but he's been sober for 11 years, and is a great dad now. My mother who had also done some very questionable things as I was growing up had for the most part been a good parent. She still does far more than I think she should for me even when im 34 years old. I've always planned on helping my parents as they aged. I still do. I go and do yardwork at my moms house when she needs it. My dad lives several hundred miles away, so i can't do much for him, not that he needs it. He's 67 and in great shape mentally and physically. My mom is doing okay, she has what the doctor says is arthritis in her arm. She can't start the lawn mower or weedwacker by herself so I have to go over and do that stuff. My question is when they aren't able to care for themselves, am i morally obligated to care for them?

Are adult children morally obligated to care for aging parents?
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