Duad Charts describe the differences in Twins

Astrologers have found the charts of twins of very great interest. Twins are often born very close to each other in time, and therefore often have the same or very close to the same energy imprint at the moment of their first breath—yet so many identical twins are very different in character, even though they look the same.

One of my great interests in Astrology is genetic inheritance shown through the planets, signs and aspects. For example, a member of one generation of a family may be born with Neptune on an angle, one of their children may have a Pisces Ascendant, Sun or Moon, and their grandchild may have an emphasised twelfth house, so we have a consistent flow of planet, sign and house throughout the generations. Other members of the family are likely to have their Sun, Moon and/or ruler of an angle in aspect to Neptune, so you could say the family has a Neptune theme running throughout.

Whilst refining this system I thought I would check decanates (the division of the sign of the zodiac into three separate sections) and duads (the division of the sign of the zodiac into twelve 2°30’ sections). I was both fascinated and astonished to find that the duad system clearly described, in detail, the genetic inheritance of a family line.


Each sign of the zodiac can be divided into twelve 2°30’ sections and each of these sections are a little mini sign.

To illustrate: the first 2°30’ section of Aries is the Aries duad of Aries, the next 2°30’ section (2°30’ – 5°) is the Taurus duad of Aries, the next 2°30’ section (5° – 7°.30’) is the Gemini duad of Aries, and so on.

The first duad of Taurus (0° – (2°30’ ) us the Taurus duad of Taurus, the next (2°30’ – 5°) is the Gemini duad of Taurus, the next (5° – 7°.30’) is the Cancer duad of Taurus and so on.

So each sign starts with its own duad and moves through the zodiac in order of the signs (click to see Duad Table).

A person will be very drawn to those who carry in their natal chart the same sign as their duad.

E.g. Someone who has the Sun in the Aquarian duad of Cancer will be very drawn to Aquarians and those with the Moon in Aquarius, even though this is not a sign that is normally considered compatible with Cancerians. It is quite likely they will have an Aquarian parent, grandparent or child.

To calculate duad charts see article on calculating duads and dwads in The Duad System Menu there is also a little duad calculator that is free to download if you wish.   http://aliceportman.com/?p=606


Whilst studying the charts of twins, both identical and non-identical, that were born very close together in time, I found that the duad chart for each twin clearly showed their differing natures and to an extent, the different experiences they have in life. This article will use the charts of identical twins, Adam and Bryan, to illustrate how the duad chart system works.

You can click the charts to enlarge them.

As you can see, these two charts are nearly identical. Adam has an Ascendant of 24 Capricorn 21 and Bryan has an Ascendant of 24 Capricorn 57, so even the degree is the same for each person. Likewise, Adam has a MC of 20Scorpio01 and Bryan has a MC of 20Scorpio30. Adam has a Vertex of 28Leo32 and Bryan’s Vertex is 28Leo55

It would be hard to get charts that are more identical, but these two twins have quite different lives. One is the father of two children, the other is having difficulty starting a family. Each would receive the same transits, progressions and directions at the same time but why would these produce different results?

Duad charts give the answer!

Adam’s duad chart

Adam’s duad Ascendant is 22Libra12, indicating that he will be drawn to those with Libra rising and planets in Libra, particularly if they are around 22°. He has no close aspect to this Ascendant, so no planets are influencing the way Libra rising expresses itself. This Ascendant will give charm and a desire for beauty and harmony in his life.

The ruler of the Ascendant, Venus, is in Libra in the 12th house, suggesting that he would value his privacy and require quiet times to regenerate his energy. Venus is trine the duad Aquarian Sun, increasing his charm and harmonious presentation to others.

His duad MC is 00Cancer07 indicating a desire to work with the public and/or nurture others. Ceres is in close sextile to this MC, suggesting that the nurturing tendency would be quite strong and perhaps gives an interest in cooking (Cancer) healthy foods (Ceres in Virgo). The duad MC is also sextile the North Node, giving an interest in working with others, perhaps in community or family groups.

The ruler of the MC is the Moon in Sagittarius in the 2nd house conjunct Mercury, giving a need to make money (2nd house) through communication and/or trade (Mercury). As Mercury is ruler of the 9th and 12th, this could perhaps involve publishing or overseas interests.

Adam’s Vertex is 12Cancer29, quincunx Mercury which increases the power of this planet. It is also square Venus, increasing the power of his Venus in Libra, and adding to his charm.

These signs and degrees would always be important for Adam and may respond quite strongly to transits. He would find that he had a particular affinity to members of the family who have their natal planets or angles on his duad degrees and would be attracted to those whose natal chart echoed his duad chart in some way .

Bryan’s duad chart

Bryan also has a Libra Ascendant, Cancer MC and Leo Vertex in his duad chart, but the degrees are different and this difference brings into play an entirely different focus in life.

Bryan has the difficult, temperamental and stubborn duad Mars-Uranus conjunction in Taurus quincunx his duad Ascendant. It is also on the cusp of his duad 8th house, bringing pressure in the areas of joint finances. This configuration is square the North Node, further suggesting that there would be difficulties with financial affairs involving family, groups, and partnerships, particularly as Mars rules the 7th cusp and 2nd cusp.

Bryan has duad Saturn in Capricorn square his duad Libra Ascendant, bringing some restrictions into his ability to express himself harmoniously, and as Saturn is in his duad 3rd house, perhaps some problems in dealing with siblings. Saturn is also quincunx the North Node suggesting flexibility and adjustment is needed in all situations connected to siblings and family.

On the plus side, Bryan has duad Jupiter trine duad Ascendant and conjunct duad 5th cusp. This is helpful in self expression and beneficial for producing children. As it is conjunct duad South Node, it suggests that he has a karmic connection to his children. Jupiter is ruler of his duad third house, so he would love his brother, despite the difficulties described by Saturn in the third conjunct 4th cusp.

Bryan will be more responsive to the 28-30° placements with transits etc., than his brother Adam, as these are brought into prominence by his duad Ascendant degree.

So you can see that even with a birth time difference of only two minutes, the duad charts describe two very different people, with Bryan having a duad chart that shows a great deal more pressure and tension than Adam’s. Each duad chart emphasises different degrees and therefore different planetary placements.


These are shown when duad planets and angles connect to planets in the natal chart. They put much greater emphasis on both the duad and the natal planet, so when transits, progressions and directions activate these positions there is often a strong reaction.

Adam’s natal chart is on the inside and his duad chart is on the outside of this wheel.


You can see that the duad Pluto is conjunct natal Scorpio Sun at 8-9 Scorpio. This puts considerable emphasis on both the natal and duad placement. This degree will be highly responsive to transits etc.

Likewise, duad North Node is conjunct natal Vertex at 28-29Leo, emphasising this degree for transits etc. As this degree also resonates to the Ascendant in Bryan’s duad chart, the transit triggers may affect him a little more than his brother Adam.

Adam’s duad MC is square natal Venus, so the natal Venus would resonate more to Adam when activated by transits, progression and directions.

Bryan’s natal chart is in the inside and his duad chart on the outside of this wheel.

Copyright (c) Alice Portman 2009

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