It is clear that you are not a responsible cat owner. How are you expecting to pay for 12 sets of neutering and vaccinations and vet care? Do you know how much that costs? The first thing you have to do with a new cat is get it checked out, neutered and vaccinated:

Neutering: QR300 minimum
Vaccination: QR540
Deworming/Health Check: QR150
Total: Approx QR1,000 per cat
12 cats: QR12,000

Your parents are happy with that cost? I highly doubt it. And that's not including all the food, litter, toys, collars, ID tags, micro-chips and emergency vet treatment that will be needed as well.

Just because you've taken them off the street doesn't mean they have a good home. If you don't have them all fully vaccinated and one of the gets sick, they will all get sick, and if you don't get them vet treatment, some diseases can kill them.

www.qaws.org