What is the proper age gap between kids?

Hey I don't feel there is any perfect age gap between siblings as long as it is not really huge, such as almost 10 years or so. My kids have an age gap of exactly 6 years. Most people say it's too big, but they are perfectly happy with each other. Then again, I have seen twins who can't stand each other and even siblings with a gap of 2 years who are always fighting. So for me, as long as Ur able to make the kids be loving and friendly towards each other, the age gap won't really matter