My very first thought when pondering this question was…”a feeling of HOME”.
Of course there is no ONE standard but there is an inherent comfort & sense of familiarity in twin unions that is not typical to karmic relationships in that the latter tend to be mirror reflections of our polarities, whereas the former tend to mirror similar imbalances.
Twin unions also frequently and perfectly complement each other’s skill sets, talents, and life passions…the ultimate yin-yang/masculine-feminine expression… and when in complete balance work together to co-create their own version of “heaven on earth”. That said, in the beginning stages this complimentary dynamic may not be at all evident…that is, until each partner becomes authentic to their own lifestream, void of all external influence and solidly anchored in their soulular expression of Self.
The merging of a twin union has everything to do with our own internal m/f merging process…ie, when we embody internal union, we externalize that union….and is therefore one of the results of our ascension process.
Depending on our personal soul plan for balancing karma and transcending core wounding, some people ascend with their twin, some don’t…but in both cases, and in an effort to help each other GOD realize, the complete union doesn’t take place fully until each is fully balanced within their own m/f polarity.
Because of our commitment to Christ attainment in this lifetime, those in soul union relationships before ascension have one goal in (higher) mind: help. each. other. actualize.
This divine commitment can be rigorous and acutely challenging (even temporarily volatile) in the early stages, especially if there are stark, contrasting belief systems in place…ie, opposite upbringings/outlooks/religious affiliations, etc….but the higher Self only cares about harmonizing and balancing each other, so there is a tendency to push and test each other’s limits like no one else has or ever will. In the event that twins come from “opposite walks of life” (opposing ends of the polarity spectrum), the point is to meet in the middle in order to neutralize and merge into zero-point.
Because of that twin flames will go to hell and back together and the relationship will survive the seemingly insurmountable. This is because the union is deeper/higher than the earth connection and so the typical human relationship constructs don’t hold water. ie, what is divinely ordered can never be lost or broken…only delayed.
Overall I would say…it’s familiarity not similarity that binds a twin union.
Too often I find that people are looking for someone who will reflect their sameness, when in reality, our other half will compliment us thru our differences….those missing puzzle pieces are the places to seek the familiar.
Lastly and most importantly…trust in your heart’s knowing!