Ultimately, between now and eternity, everyone and everything is our soulmate, including plants, animals.
There is no one and only soulmate, except temporarily over a few lifetimes. Otherwise, this would exclude other spirit beings. Soul relationships are inclusive, not exclusive. Just as there is no one food or vitamin except over a few meals, we need variety in our psychospiritual nourishment. All spirit beings are beautiful, but only a few are currently attractive to us because they have chosen or been endowed with a physicality which resonated with our current needs.
Resonance is the subtle synchronised interaction between two or more individuals whose frequencies overlap. Consequently each entrains the other.