I am so sorry that I've missed this post, because we have been infected by a trojan for the last two days...
I know you've written about your parents in another thread before (at least it was a hint on their situation) and I am sorry your mom is seriously ill now and can't take care of your father...one of my friend's dad has dementia, too and it's a fulltime job for her to take care of him...
So {{{{{HUGS}}}}} to you to have enough strength...

As for the cat, I think you already know deep inside what would be the best in your current situation...I know it's always hard to go to a shelter and see all those unwanted beauties and I feel always bad when I returned home without taking one in.
If you decide to take the new kitten in I wish you the best of luck, if you decide against it, because of your current situation and maybe because of Ripley, Scout and Jazz, try not to take it to hard...we cannot help them all and it's your very personal decision how many cats are meant to share your life...you've already taken in three wonderful cats and also Disney, you've started to help the cats with sewing blankets, you've made already plenty of cats happy...


Whatever you and your family will decide on this I wish you the "Best of Luck" and listen to your gut feeling!!!