No doubt you've seen the sign:
(image courtesy of pixabay.com)
Here's how I look at it: the Gemini symbol is made of two complete one's put together. In other words, if Gemini is the symbol for Twin Souls (and if you read The Gemini Bond, you'll understand), then it is necessary for each Twin to be complete in and of themselves before they can join. Each one must become fully One before they can become Two-in-One. That's what I take from this symbol.