The sign of Gemini is a sign of MUTABLE quality so it is rare for two of them to stay together for very long. It is not that they can't form long relationships, but when they collide, it's as if they inspire each other to change. Their Air element gives even more speed to the process so they will probably not stay together for very long, but rarely regret it or see one another as their one true love.
Gemini is ruled by planet Mercury, so in this particular case we have two Mercury guided persons together. This looks more like there are four or even more people in one relationship so it makes it hard to find focus and ground the relationship into something more serious. There is not much they can do about it, especially since they both enjoy their nature so much.
Air element, that they perceive as if it gave them wings, has trouble understanding the other, thorough, Earth side of Mercury related issues. It is to be expected that they will have fun, though. As eloquent as they are, they will never run out of topics to talk about, however superficial they might be in their conversations.
They usually enjoy each other's company pretty much, so even when they move on from their romantic relationship, there is a great chance they will remain friendly. That is, if they had anything in common except their Sun sign to begin with.
Do you wonder how to conquer his/her heart? Get tips about Gemini here.