Here's a common question astrologers are asked: If twins share the same birthday, how can they sometimes be so different? Isn't their birth chart the same, too? The answer is ... no! We expect two people born at almost the same time, with similar genetics and raised in the same environment to be very similar. And most of the time they are, but it's the exceptions that are used to challenge Astrology.
Look to the Rising Sign
Individuals born on the same day and year will have many astrological factors in common. Still, there are fast-moving patterns that can make a difference in just a matter of minutes. The most common is the Ascendant, also known as the Rising Sign. This is the point rising in the East at the moment of birth, which plays a great role in shaping the way a person looks and presents herself to the world.
This rapidly moving point, which is the cusp or border of the First House, is based on the Earth's rotation on its axis, so that each of the twelve signs will rise during some two-hour period of the day. Twins born several minutes apart may have different Rising Signs. For example, I had twin clients, one of whom was a Taurus Rising with the patient steadiness of this Earth sign; the other, born about a quarter hour later, reflected the chatty bounciness of her airy Gemini Rising.
Separated at birth
There are many known cases of twins separated at birth who have parallel experiences in life, including the same dates for events like marriage and the births of their children. Twins raised together like the Epstein sisters born on July 4, 1918 can grow up as distinctly separate individuals who wind up in the same public role: in this case, as the famous advice columnists Ann Landers and Abigail Van Buren. Then there are Robin and Maurice Gibb, who look very different but shared a professional life together in the Bee Gees.
There are also individuals born on the same day and year who are very different from each other. Margaret Thatcher and Lenny Bruce, Sylvester Stallone and George W. Bush, are famous examples. They were not born at the same time or place, so could be significantly different astrologically
Same birthday, different traits?
There is yet another factor that explains why twins with essentially the same astrological charts can appear to be so different. The chart is an expression of raw materials, traits or qualities that can be expressed in a variety of ways. One person with assertive Mars in passionate Scorpio can use this intensity as a healer while another might apply it with avarice or cruelty.
The chart doesn't say who one must be; it describes the energies with which one has to work. Twins have a need to differentiate themselves, to become true individuals. The desire to be distinct is common to all of us, but may be an especially compelling drive for a twin. There is a natural instinct to differentiate oneself that unconsciously motivates one twin to choose a certain type of expression of a planet in the chart while his or her sibling chooses another. They are working with the same ingredients but mixing them in unique ways. Twins, even those who are very similar and remain close throughout life, are separate people who will live out their birth charts in individual ways.