which factor in the natal chart shows birth of twins?

I'm a twin, born two mintues from my sister. We are fraternal and don't have similar appearances (body type, health type, etc.) Our moons I think are identical, in fact that are few differences in our chart (though I can't remember). There are slight differences somewhere though. I don't think we have the same "fate" exactly. I am not sure that's what natal charts are about. I think it's more about how our energies express themselves through life, but different situations can occur to express a similar energy in a similar way--but it may look quite different. But I do notice analogous things that happen in our lives though we treat them wholly differently from oneanother. We just have different ways of thinking in some respects, similar in others. One of the major differences I think I notice between us though is that we have different karmic origins. I suspect we have probably had similar past life experiences (if you want to take it that far), but again, we've been totally different, and whatever we need to express in this lifetime, though maybe a very similar lesson, I think is going to hit the two of us in two different ways. We don't absorb our world quite the same as the other. If that makes sense. We are on two separate paths, but analogous events or patterns do certainly occur between the two of us. (relationship patterns, education patterns, etc.). But she is organized, scientific, I'm abstract, creative. So it's weird, different parts of our charts also express themselves through us in different ways. Like we are a different kind of filter expressing the same energies but the output looks different.

twins are not born at the "same time" otherwise they would be born together.

and I mean TOGETHER, not even a second apart.  this does not happen.

astrology does not have all the answers, that is my light for this observation.

In short you are good mirrors for one another.  I find this interesting, thanks for sharing.