Composite chart is an artificial chart. You, or your program calculates midpoints of planetary placement in each individual birth chart and chart you get as a result is brand new chart of your relationship. It is actually birth chart of your relationship. We read composite chart, as a chart of separate entity. However, you have to be skillful to read composite chart properly. From my experience composite chart really reflects on what will happen. Composite is a big picture of the relationship and it is really composite what tells the story. Sometimes I am asked about Davison chart, which is very similar to composite and the way it should be read. So, whatever version you decide to use, these rules apply equally.
Relationships that are fated or destined to fall apart can be read in composite as well. With composite you have to be careful and bear in mind that two people are affected by each aspect and planet placement with the same resonance. If you have difficult Pluto Mars aspect in composite, you equally are acting out Pluto and Mars at the same time. Taking this example, I can tell you straight away that if you guys survive this without any harm, you already won. Power struggles, triggers that are much more stronger than one human being, and sometimes violence is present here. If you have this aspect natally, you are prone to this behavior anyway, so with this composite you get a chance to make it or break it. It is not common to see this one in healthy relationship. Initial passion is very quickly turned into hatred, never ending arguments and fights… just to name a few.
Aspects in composite are way more important than synastry aspects when assessing how your relationship will really look like one day. If you want to predict outcome, the end or any potential crises which will come anyway, you should use transits to your composite or davison chart. It works very accurately and precisely in predictions. I also check transits to both birth charts and secondary progressions of one partner to birth chart of the other and vice versa. This works very well as well. If you are able to combine all these things, where, very often one leads to another or confirms what we have already seen in birth chart transits, we are really able to tell how story will unfold.