Mother’s intuition
Ask any mother and they’ll tell you that they have a sixth sense about their children. Moms know when their child is in trouble, even if they live in another country. There’s probably no scientific evidence behind this, but there are quite a few anecdotes to be mere coincidence.
Anyway, this tight-knit family was supposed to have dinner at their mom’s place. It would have been the OP, their brother, sister, and mom, but the sister was a no-show. Mom had a gut feeling that something was wrong, and after realizing that nobody had heard from her (they even asked her ex-husband), they decided to break into the sister’s apartment, only to find her sprawled on the floor after suffering a major stroke. She survived, thanks to their heroic act and a motherly gut feeling.