My older sister and I have the same Taurus ascendants, to the same degree, and the same MC, IC DC and Vertex, all TO THE SAME DEGREE AND IN THE SAME SIGNS. All our angles are identical. However, she's a Cancer and I'm a Sag (though I have a close Sun/Neptune conjunction in my birth chart, so I'm watery too) and we have planets in many different placements. I tried to make friends when we were kids, and one of the biggest wounds of my life was the fact that she absolutely detested me with such a passion that I, and others, were bewildered by it. She couldn't even stand to be in the same room with me, as if she was physically repelled by me. But everyone else raved about how I was such a cute friendly child who was loving and tried my best to please everyone. Everyone else seemed to love me and I couldn't figure out why my sister was the opposite. In fact, she told me that if I hung out in the same room as her, she would hit me, and it would be my own fault. (She did too, often.) The rule was, if I had to pass through a room she was in, I must do it quickly and not look at her.
She is well known in our family as a harshly critical person, and in fact she has cut most of our family members out of her life for various "infractions" against her values.
But you would think that with our charts virtually identical in so many ways, that we would be soulmates. But maybe because our angles are identical, it creates some astrological version of magnets turned the wrong way, repelling each other? I did try my best to please her when we were kids, and I admired her very much. I was more than willing to make friends with her, but she wouldn't even consider it.
We have a younger sister, and the two of them get along as long as the younger sister does everything our older sister orders her to do, but our older sister absolutely detested me from the moment I was born and when people questioned her about it, she could never explain why. She was just emotionally and physically repelled by me. We've had no contact for over two decades now.
Her North Node is exactly conjunct my Juno, but her South Node is conjunct my Arabic Part of Nemesis (not the asteroid Nemesis). My North Node is exactly conjunct her Part of Fortune. Her moon is closely conjunct my South Node. All of these would seem to be soul mate, best friend aspects (except for South Node/Part of Nemesis).
My study of our synastry has caused me to question the validity of synastries in general; unless astrology only shows the energy available in the combination of any two people--but not how the people will use that energy. Some of my closest long-term friends and I have Mars/Uranus/Saturn conjunctions in our synastries, which would seem to be explosive, but in fact it has manifested in powerful commitment to each others' development and the attainment of our goals, in strong partnerships.
Right now I'm looking at the synastry between me and a man I'm interested in being romantically involved with, and because of my study in synastries with people in my family and among my friends, I don't think I can tell in any way whether or not this man and I would be good partners--because regardless of the energy available to us, astrology can't tell us how we would use that energy.
I would love to hear others' opinion of the meaning of my synastry with my older sister, and any conclusions you've come to through studying the predictive value of synastries in general. Thank you!