How do I convince my parents to get a cat?

Ok so I live in a villa and have my own garden, and there comes about 10 cats and I am able to touch at least 4, and one of these cats is a house cat, I can tell since the first day he came in the garden he was wearing a Necklace around his neck, the next day it was gone because most probably he tore it of, he has been coming ever since the summer holiday, he still comes and the poor thing sits and cuddles next to the window that is the closest to us, we feed him and he is house trained , and our cousins have a cat the same breed only a different color, our cat is silver and white and my cousins is brownish, everyday it walks with me to school and at some point it goes back to the garden, when my mom used to go the collage I used to let it in for a few minuets then i get it out, it’s school time and the first semester is going to end next week (Thursday 17th) so any can anyone suggest something to tell my parents?