Well, if time is truly a physical measurement, then I think its extremely likely that they would exist. Think of it this way:
If our universe is whirling through time/space, at whatever rate it does, you would think that there would be something next to it.
I find it hard to believe that we would be the only universe if thats really how things work.
Last I knew, that was only a theory (although, there is some proof that time is a physical measurement, not a perception, I just dont understand it enough to explain it).
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Kids in the back seat can cause accidents.
Accidents in the back seat can cause kids.
Moral: Drive a two seater