I will try to answer your question as best as I can from my personal experience with my own twin, though warning! This post may get long... :)
First things first, yes, I absolutely believe in twin flames having met mine in this life. I also believe in soul mates, or soul families. I do not believe anyone other than each separate individual can determine whether or not someone else is or is not your twin flame. There is no absolute formula for figuring it out; however, as I have experienced it with my own twin, there have been things I've found to be true and others which may or may not have been written about elsewhere. So I'll share those for interested parties. I do not; however, believe that it means my experiences or situation will hold true for each and everyone else. Ultimately, as frustrating as it may feel when you have not met your twin to hear these things, if you are supposed to meet them you will know them when you are supposed to. The relationship of twin flames, I think, is often so idealized and blown up into almost a Harlequin romance novel, or Pride and Prejudice, but that's just not it. I mean, it COULD be for some, I would not rule out the possibility entirely, but it does sort of defeat the purpose of the relationship. Which is to ultimately grow spiritually. A twin flame is not your perfect mate or romantic partner, they are your perfect mirror, the other half of yourself. And they are just as human and flawed as you are.
Now, whether this has any bearing or not, I can't be absolutely certain, but I believe it does. It is not something I've read before (to date) but it holds true for me. I am an artist, and have been an avid reader and writer since I was a child. One of my favorite stories growing up has always been Peter Pan. Literary analysis aside, as a child I used to make wishes on stars in my window and stay up waiting to see if Pan's shadow would come for me. I also had the idea that my own shadow could leave me, or had its own personality. Growing up, and learning a bit about the idea of romantic soul mates (and being an anxious hormonal teenage girl) I wrote stories about lovers parting ways, drawing straws in places like St. Augustine or Paris, and walking the circumference of the world in opposite directions to see if they'd meet again on the other side. Another I wrote, was about a man and a woman whose soul had been split before birth and who found one another on Earth through a painting the man created of the woman. That he was haunted by images of her and eventually painted his way to her. This was long before I ever knew what a twin flame was.
I am also the mother to twins, with twins on multiple sides of my family (not the twin flame kind though!) and it was believed my mother may have conceived twins when she conceived me, and lost one early on. I'm a left handed Aquarius, though I was due the second week of March. I was actually due within a few days of my twin flame's birthday.
These things MAY be nothing, but to me they add to the rest. Some places I've read numerology can be an indicator of twin flames. I'd like to stress I don't believe it is always the case or a hard fast rule. Again, only you can truly know. But with my own twin, we share the same life path, destiny, soul, hearts desire, personality, maturity, and balance numbers as well as our karmic lessons and karmic debt. We were also both born with first names we do not like, same amount of letters, same first letter.
Our life experience has been similar. We both had similar relationships to our parents respectively. We are both the eldest of two; however, he is 17 years, 11 months, and 1 day older than me. Which happen to be 3 significant numbers to me as they relate to my children's birth dates, my birth, and my lucky numbers.
We both share similar tastes and interests in history, antiques, vintage things, music, books, etc. Yet it's different enough that we can learn from one another. We share similar values and both place importance on tradition and our ancestral history. We also have a similar heritage. Actually, we sort of look similar. We are both taller, lean (I'm more thin), pale, freckled, with well define bone structure, and very dark thick hair.
When we met, it wasn't immediate sparks. There was no love at first sight (for me) but there was curiousity. He seemed unreal, like something I'd imagined or something I couldn't really touch. It seems strange because I still feel that way, like he's both flesh and blood and also (here's how I wrote it once) "the reality which outdoes the dream until dreams begin to dream of him."
It took time. We were both intensely curious but cautious. Once things began, they happened very fast. It has been a romantic relationship for us, but romantic doesn't fit right as a word. In fact, we are both artists (he's a musician, and I write and draw) and yet as much as either of us is inspired beyond belief by the other there are never enough words, sounds, or images to answer the burning question of "WHAT is this?" There is no satisfying the question inside. It's a continuous yearning, so much so even separation and the pain of loss did not sever those ties. Quite the opposite.
Its been like realizing he's just a man, a flawed one, he makes me furious, he hurts me, and yet I understand. I can feel it deep inside of myself. Every emotion is heightened beyond anything else I've felt, and it's the same for him. It's like loving with a wild animal living inside your chest. There is understanding even within words. Even with separation and time without apologies we reached forgiveness and closure, and growth.
Sex, ah. Yes. I don't recommend wanting to find your twin flame solely for sex. But it is different, entirely. For me, it was the sort of experience that once it happened, I genuinely couldn't recall being with anyone else. And once we were apart, I had an insatiable appetite for lovemaking but found my needs unmet by anyone else I was with, and sex was unsafisfying. I also found just like when we were together and I could feel him without being physically touched, it was the same apart. I knew when he was nearby.
And I knew from a distance when to contact him, when something wasn't right and he was thinking of me. Which led to our reunion after separation. Which, is not normal, and I'm very aware may not last forever. Which is okay. Because even if we do separate and it is painful again, we will never stay separated forever. We will always find one another again and again, and I do find peace in that knowing.
Reuniting, is to me, better than meeting. I learned about twin flames as more than a passing word here and there when we separated and I stumbled across it. Seeing him again, it was in a city we never went to together but always said we would. And when we touched, it set my entire lower back tingling and prickling and burning. Like I kept pushing towards him and trembling. It's difficult to describe accurately. It felt so much like home when for two years and some I hadn't felt at home anywhere. We were embracing, and he kissed me for the first time in that long, and pulled back to look at me and said "I could feel your heart." Yes, because it was going crazy! I had the thought at that moment kissing that it was way too fast and hard, I wasn't sure it was just mine!
There were many other things to the reuniting, including learning we'd both made many mistakes after separating and had to work through them, but we had. We also still have things to wrap up if we intend to be together. More so on his end than mine as I am free to do as I please. But I've told him I am here. I have heard his desires, and I know he says he won't lose contact with me.
The twin flame relationship is beautiful because it is challenging. It is perfect in its imperfection. It's about coming into your own, because your twin flame is separate from you but they are a part of you too! You cannot only take the good and avoid the bad, that's not how it works, and you both have to be ready. There may or may not be synchronicity (if that is something you pay attention to, I do and have experienced it as well as other things). The whole runner and chaser thing could actually just be how you or your twin deals with relationship problems, it may NOT follow a formula.
Ultimately, it isn't something anyone else can answer for you or you can tell anyone else. They shouldn't either! Only the individual can know, truly, at a soul level their own twin. Reading Rumi makes me think of twin flames, so I'll end this with a few of my favorite quotes.
"The beauty you see in me is a reflection of you."
"If you find me not within you, you will never find me. For I have been with you from the beginning of me."
"Your task is not to seek for love, but merely to seek and find all the barriers within yourself that you have built against it."