Thank you all so much for taking the time to respond.
My younger DD who lives with us, works full time & we provide before and after school childcare for our grandson who is in kindergarten. The divorce , and the events leading up to it where traumatic; we had no choice but to take them in. Sadly, the breakup definitely left it's scars on my grandson, who does have behavioral issues; he is quite a handful ! DD hopes to find a place of her own, but this will be a significant financial challenge. My parents do have health issues, and I am afraid that this situation will put them both over the edge. DH does what he can to help out, but I'm basically "it". Older DD's new job is in healthcare, and will have erratic hours. Her newborn was a preemie, and he does has some health issues.
As some of you have pointed out; my older DD may be put out if I do not provide childcare for her son, since her sister lives with us. This is my biggest fear; I do not want to jeopardize our relationship, but at the same time, it is already high anxiety around our house. Under the circumstances I know that my mental health would most likely suffer. In my heart of hearts, I know that I am in a no win situation; I may have to agree to do this keep the peace.