Hi Eric, sorry to hear about your situation and struggles. Having such things happen to such young people is always a difficult thing. I had a family member that died of a brain tumor when they were young and it is a very hard thing to deal with, including the trauma that occurred before they died.
In regards to asking others for help, starting a new relationship is usually best done when the relationship is relatively equal. It may not be true but there seems to be an implied burden in accepting you. If its not true then a rewording of your request may help I think. If the burden is true then you may limit who will be interested but there are a lot of caring people out there that have the energy to help families like yours and I hope you can find someone.
I'm not sure if this is the best way to say this, I'm not the most delicate person and if I have offended you I apologize. Good luck and keep up the learning if you want this lifestyle, it will pay dividends whenever it does happen for your family.