In my opinion, you could have more than one soulmate and it doesn't have to be something romantic. It's just a connection if you need to learn about each other, and when the lessons in your relationship are over you can move on naturally. Soulmates not necessarily have to spend their lives together. ^^

someone with whom you connect on a spiritual level

It is someone, with whom you have one soul for you two. You share this soul with him (her) and (s)he shares it with you too. This is necessarily mutual. How many? It depends. There may be many soulmates, I think. Of course, most often there are at most one soulmate. It is very hard to meet even one!

soul mate = 知音. You get the picture.

Hi Miya. A soulmate is someone that you have encountered in many different life times and have loved many times. That is why the first time you meet them in this lifetime you feel as if you have known them forever before you even knew their name. I think that there can only be one soulmate.