Finding Lon Values that are close together on uneven lists

I have two matrices of Longitude values. I would like to identify points that are close together within the two lists. My problem is the lists are of different lengths

One of them is named Lon_pair and the other is named Lon_epa.

Lon_pair is of size

size(Lon_pair) 
12635       1

Lon_epa is of size

size(Lon_epa)
20560       1

How do I find points within Lon_pair that are close to those within Lon_epa? Or find the difference between them?