Some pet cat, who lives outside independently, gave birth at my stairs. I tried to get close but the mother cat got very aggressive. So I want to know or learn how to get close to these kind of cats so I can keep them as my pets.
Patience is the key to success
Food is the best bet to make bonding. Put tasty cat food like meat or fish at a distance and watch it from even further distance. If the mother cat doesn't eat the food the first day, wait patiently for two or three more days.
Once cat eats the food. Give it regularly for about 10 days and sit at a distance and watch her eating. Cats also keep shifting resting place of babies. So try to follow.
Slowly try to move closer to watch the cat eating. Don't be too quick. The cat will slowly get habituated to your presence.
Now you will probably be able to watch the kittens from a distance. The mother cat will not get aggressive. Also the kittens by the time will start exploring the territory. If one comes near you just give your finger to the kitten to chew. Do not do anything that might make the mother cat suspicious. Like don't try lifting the kitten the first day itself. The mother cat will be at a constant watch.
Try spending more and more time with the mother cat and the kittens every day. You can also try giving the kittens some treat.
In this way after the kittens are about 2 months old, they will be very familiar and friendly towards you. By that time mother cat will also start giving the kittens some space and not keep them under constant watch. It is time when the mother leaves the kittens to make them independent. You can now probably try to adopt the kittens.
GOOD LUCK :)