Extenuating circumstances

I’m in the process of applying for vacation schemes and am worried that I’ll get rejected as I have poor A-Level results because when I was about to take my exams my younger brother fell ill and was in intensive care for two months.

The whole situation was very upsetting meaning I really struggled to focus on my studies. Do you think this is a legitimate extentuating circumstance or will firrms think I’m making up excuses?