GPA isn't everything but do colleges actually care for explanations?

I am planning to apply to California universities where freshman year isn't counted, that however puts more weight onto sophomore and junior year, the first half of sophomore year I had a GPA of around 3.6 (I am not sure since I am international and my countries grades are notoriously hard to translate into GPA). The reason for this is that where I am from you only choose your core subjects in junior year which means I have some classes I suck at that I have to attend up until junior year. My sister was diagnosed with a deadly genetic disease and I had to be tested too as there is a 50% likelihood of me having it too. This happened around the middle of the first half of sophomore year. After the worst 3/4 of a year in my life, my sister got an experimental hormonal treatment that seems to work. I am lucky to be healthy, but I did have to cook for her, make sure she takes her meds, etc. This has led me to a GPA in the low 3. Area. I have run some calculations and the best possible outcome for me is a cumulative GPA of 3.6 at the end of junior year. This totally destroys my plan to apply REA to my dream school. I know GPA isn't everything and that admissions are holistic. This is also not supposed to be an excuse for me slacking, I had family business that was simply more important than my French homework. I do believe however there is an unofficial cutoff at my dream school in California. Without naming the school and without considering my extracurriculars etc., do colleges/universities actually care about an explanation you give in the additional information section?