It is difficult without actually reading your energy and the energies of these two other people but I'd like to help you so I will look. Let's see...
You seem in love with your soulmate to whom you're engaged to be married. As a matter of fact, you have a wonderful, truly beautiful connection. I also see the energy of the one you call your twin flame though, and I can see that you do in fact have a rather strong attachment to them as well.
It is not a "better" attachment, only a DIFFERENT type of attachment.
First, TRUE Twin Flames always come into Twin Flame Union. While this may not be in the time frame you might prefer, it still happens. WHY? Because Twin Flames always come into union for a good reason: the divine mission, which is the reason that twin flames exist in the first place.
THE TWIN FLAME DIVINE MISSION - If you don't know what your mission is yet, don't worry because it will reveal it's self. You certainly have the desire to help others and to do something great, so I have no doubt that you will.
Twin Flames are exactly like soulmates, only twin flames share a soul and are one whole soul being together. Twins also share a chakra system, although housed in 2 separate human bodies: one half male energy and the other half female energy. Soulmates on the other hand can connect to one another through their respective chakra cords, creating a feeling and experience quite similar to the twin flame soul merge.
The Twin Flame Divine Mission: The reason twins exist at all, is intended to raise the universal vibration as a collective. All twins come into union and all twins engage in their respective missions, collectively, resulting in the raising of the universal vibration which in turn, creates universal unconditional love, peace and healing. The mission is specifically, to lead the masses back to truth and origin. Again, this is achieved through their mission. Each mission is unique to each twin flame soul part, and the twins together engage in the mission which merges as a collective for this very special purpose.
Your divine mission can reasonably be absolutely anything, and will be unique to you. And, will be unique to you as a couple. Your mission will merge with that of your twin flame, creating your divine mission and your divine mission will merge with all other twin flame missions as the collective.
“I'm getting married with a soulmate…”
Are you certain this other person is your Twin Flame? If so, then you'll easily be able to answer the following question: What's the twin flame Divine Mission through which you initially connected in the physical which you're both presently engaged in?”
“I miss my twin flame so much…”
Refer to the above.
“How can I overcome this?”
Again, refer to the above and also ask yourself why you are presently engaging with a soulmate versus your twin flame? While it's true that most twin flames are in union at the present, not all are. What part of the journey are you present engaged in at the moment? If you've been stagnated in the runner / chaser phase of the journey for sometime but have yet to achieve union, perhaps it would be prudent to look into the reasons why.
All twin flames come into union for the purpose of their divine mission which is the purpose behind twin flames existence in the first place. This twin flame could reasonably be a counterfeit twin flame or the real twin, depending on your situation.
I met my own Twin Flame during a time which we were both married to others. I got my divorce not because of my twin flame, but because I knew it was the right thing to do. My twin flame and I didn't communicate during that time for good reason. Then, he made himself available by getting his divorce and reached out to me to let me know he had filed it. I didn't “wait,” I simply put it out to God and the universe God made that I wouldn't wait beyond that year and that date of December 15th. His divorce was finalized on the 16th of December that year. Okay, I gave him that one extra day! We've been in union ever since.
The good thing is that the universe will make happen what needs to happen in the time frame it needs to happen — but not always in the way we expect.
If God and the universe have sent you a certain soulmate to enjoy it's for good reason. Perhaps you are intended to receive soul lessons from this soulmate or growth in some way. The Twin Flames typically connect in the 3D physical realm at a time they're READY and not before. In my case, my twin and I were already on the verge of filing our divorces. We were not on the verge of marrying others or currently truly happily married. My twin told me he was happily married but a few months later he's calling to say he's unhappily married and divorcing. Again, connecting at the right time.
Is it possible your soulmate is your Twin Flame and your “twin flame” you miss is the counterfeit twin flame?