If this question has been asked before i'm so sorry. I missed it. And if the writers said something about it then for sure i have not seen it.

But what do you think about that? And what about Daniel? Was he Regina's soulmate when he was alive? Or was Marian ever Robin's soulmate? If she was & her death meant that Robin would find another soulmate *Regina*, now that Marian is back what happens?!

Part of me thinks he has two now. It's like, on one time plane it was Regina and on another it was Marion, those time planes were never supposed to touch, but they did.

I don't know hehe :p . I think Daniel was her first (+only true love) before she met Robin . I always saw Daniel as her "high school" love but because since that period of time she was never allowed to be fully herself (& she was also stronly traumatized by his death and the fact that her mom killed him) she never gave herself a chance to see that love is possible .
Since pixie dust said that Robin in her soulmate "and pixie dust never lie" i think that he is ;) . Also when Regina was led to him ,I'm assuming Robin haven't even met Marian so if Regina had walked in they would propably feel a mutual attraction . Tink said that the fact that Regina never walked in also ruined Robin so I guess Marian wasn't/isn't his soulmate .
And I think that we might get something this season ,maby a TLK (like Snowing ,Rumbelle & Phillaura) showing once again that they trully are each other's soulmate ;) idk maybe Elsa frose one of them and the other would have to wake the other up or whatever ...

Well he was married to Marian and seemed pretty happy with her.

A soulmate (or soul mate) is a person with whom one has a feeling of deep or natural affinity. This may involve similarity, love, romance, friendship, intimacy, sexuality, sexual activity, spirituality, or compatibility and trust.

Having this in mind yeah maybe Robin & Regina could be soulmates but not in a loving/romantic level.
As for the "pixie dust never lie" thing don't forget that it was a stolen one so it may not work 100% as Tink believes.

Daniel was Regina's first love but not her true love. As for Robin for me Marian is his one true love and no matter what this show tries to do I will never change my mind on that not even for Regina's sake!

^ As much as i love Robin&Regina, i don't want them to tell us either that Robin didn't really loved Marian or Regina didn't really loved Daniel....

Difference between True Love & Soulmates --->

Edward: True Love is when you truly love somebody & Soulmate is the idea that there's only 1 person for you & i think in our show we learned that happy endings are what we expect. & so even though you love somebody, if that doesn't work out it's ok to love again.

Adam: And i think with both True Love & Soulmates there are things that you can work & you can find them. There is always hope for finding what you think is True Love or Soulmate. - ComicCon

* I STILL DON'T UNDERSTAND..... *