As they are all deciduous trees, you could consider the direction they face, and how they may shade each other in summer, or allow light in in winter.
You wouldn't want to plant them so that one completely shaded the other tree, if they are so close planted.
Nectarine and a Persimmon probably have similar growth rates and will get to similar sizes.
Depending on sun angle, you may be able to prune them to face away from each other into 2 half trees.
A Pomegranate might be a bit slower and smaller than either. You could end up with an over and understory.
Some part shade might be ok for the pomegranate, in a hot climate. Either way you should be able to prune them to advantage both.
No idea if any make better or worse combinations when close planted.