Here is the question and story behind it as sent in by The Curious 0410:

What would the relationship between 2 persons sharing similar astrological makeup, be like?
details: Hi, I arrived here from your other blog pertaining to a certain “Yamashita Tomohisa.” ;) I was actually VERY surprised someone had done his natal chart somewhere online. It’s a bit rare to see something like this.   Why am I so surprised? Well, he and I share a ~similar~ chart. I am also into astrology, and I am kind of enamored with the guy. You can see how much this amuses me to no end. Reading things about him, it almost feels like I am reading about myself; the similarities are vast and incredible… and I do say this in a humble, awestruck way when life is just full of odd miracles.  I started reading about Yamapi when I was searching the internet/IMDB/Wikipedia if anyone ‘famous’ had the same birthday as me, if not, if someone had a similar chart as my own – and where they are in terms of success and accomplishments. There were a few people who did share my exact birthdate, but not intriguing enough for me to pique my complete interest in their lives. So I looked the day ahead of my birthdate, and there, Yamashita Tomohisa, was. …. Talk about being pulled into the depths of a sinking sea. I am enamored with this guy in a strange way. (That’s my Venus sq. Neptune talking)  The reason why I looked the birthdates up was because I’m at a crossroads in career. I am seriously considering Acting – something that conflicts with my fears about media exposure(should I ever become successful at that end). It seems the young Yamapi has gone through a lot in the past years, and I can understand a lot of his troubles because they are mine as well.   My question, if you can enlighten me – and because I’m curious about my own infatuation with him – Supposedly, let’s say two people born on the same day or one day difference gets together …. What is the “relationship” like?  How would the two people in the relationship grow if they are so similar in astrological makeup? Would such pairing “stunt” their growth because the person they love, are quite similar to themselves? I am curious, because I’m sure this astrological combination is pretty rare in life – where your significant other, or crush, shares a similar chart as you… so the lessons, frustrations, joys and communication are same. I apologize if my wording is hard to understand.  Thank you, 0410  (Sun Aries, Moon in Cap, Cancer Rising at 20 deg)  PS. Please forgive my run-around-the-maze sort of thinking. You can rephrase my question if you decide to publish.

A note on similar natal charts
Similar natal charts are actually not uncommon, though it would be extremely extremely rare for two people with a lot of planetary positions and aspects in common to meet in real life. Some time ago, I published about a statement in a book about horaries which I found rather misleading. Two people having similar natal charts are basically the result of the same principle, though horary astrology aims to answer questions. I’m sure if I go dig into books that explain more about the technique and calculation of astrology, I might be able to explain this in more detail. I’ll put it on the list to post about some day soon. On to the answer!

The question that was asked doesn’t really lend itself for horary astrology as you would be questioning astrology about astrology. I prefer to answer this question from experience.

The most used theory when it comes to synastry or compatibility in relationships is that Yin/Yang should balance each other out. Too much of “easy” makes for too light hearted relationships that don’t last and too much of “difficult” makes for impossible or emotionally charged relationships. While at first glance you would think great similarity in natal charts would make it easy to relate to each other that isn’t necessarily so. It can also create conflict due to the nature of the planets involved. For instance: Sun conjunct the partner’s Sun could result in “two captains running the ship”. On the other hand it is true that you’ve acquired the same tastes and abilities, the same mental responses and the same ways of taking action or dealing with anger. The correct wording may not be ‘stunting growth’ but a question of extremes. Extreme up and downs, extreme like or dislike, extreme boredom, extreme anger explosions (… it’s not often but once Mars in Taurus gets a move on…).

Remember that you would also share a composite* very close to your own natal charts!! In this hypothetical relationship, not only the natal charts are equal but eventually the progressed composite is the same as the progression as both of your individual charts and the transits going over all three charts (natal1, natal2, composite). When one of you feels the effects of loneliness (Saturn, for instance) the other may not be able to counter it because they’re so swallowed up in the same feeling they cannot give their partner that extra push in the back they need. This is exactly because this transit is synchronously affecting the health of the relationship in the same way it is affecting your individual moods and stats.

I hope this answers your question.

* A composite is drawn for two people in a relationship to see how they function as a unit.

The below is a quadriwheel of the four of them. I’ve placed comments at interesting places.

Note that I only have the birth time of Yamapi. What that means is that the planet positions of the other three are inaccurate and could differ by a degree or two. Their Moons are unreliable, since the Moon travels about 13 degrees in a day.

What does seem to stand out is the following:

• Two of his friends aspect the axis (Asc/Desc) with their Sun’s. Statistically well done.
• Two of his friends have a natal aspect between Mars and Jupiter. Two of them make aspects to the Natal Jupiter of Yamapi with their Mars, one in the reverse and one Jupiter/Mars conjunction on the axis. Statistically well done.
• Two of his friends have an animus (Mars) / anima (Venus) planet conjunct Saturn in his 5th house oppositing his natal Mars. Statistically well done.

What also always strikes me as statistically well done is that entertainers seem to have more Sun/ Mercury/ Venus stelliums. Both Yamapi (in Aries) and Jin (in Cancer) have one. I’m also aware Kame has one (in Pisces). Toma has a Mercury/ Sun conjunction, so no Stellium. However, this is in the native sign of Venus (Libra). You do have to take note here that Venus and Mercury can never be more than 60 degrees apart, so this is only ‘statistically interesting’ if the Sun joins them.

I’m still pondering how to explain the meaning, but as said, the connections are clearly visible.