Kittens on car tyre - checks to be done before start of car

Recently, I found two cute kittens (one is grey and another is white) sitting on the rear tyre of my car. They were totally hidden between the tyre and mudguard of the car. My younger son observed these two little ones looking innocently by sitting at the top of the tyre.

From then on, I made a point to look for presence of anyone before start of car.