Dear (name):
I won't be able to attend school for today and tomorrow because i just got a call from my sister saying that our mother fell ill and is going to be in the hospital for few days. I am very sorry for the fact that i'll be absent for two days because i have to go and take care of my mother, but i'll be back in school as soon as she gets better and catch up with the rest of the students.
Thank you for your consideration
Sincerely
(your name)