"I am stunned to read of both partners having strokes withing a day of each other. Could there be any possible underlying cause, perhaps a toxic substance exposure?"
It is so weird, I know. But I don't think there is any toxicity involved. My grandmother died of a vascular event similar to my mom's brain bleed, and my uncle (mom's brother) had 2 strokes. Also, my mom had high blood pressure, and smoked.
As for her partner, he was in very poor health--uncontrolled diabetes and hypertension--and he had been having chest pain and tightness for weeks. Probably the shock of what happened to mom is what caused him to have the heart attack when he did. The stroke was caused by the procedure he had to treat the heart attack, unquestionably (it's a rare but well-reported side effect of the blood thinner the hospital used).
So very horrible, and weird, but clinically it kind of makes sense.
Thank you for your encouraging words about your friend, I hope my mom has the same outcome.