This is another one of my major concerns in this era..

If you do prayer 5 times a day in minimum because you obey Allah and Prophet Muhammad s.a.w., then for the very same reason you must stand close to the person beside you in a congregational prayer.

In the event when the 2 persons on your right and left respectively are not standing close to you, you move yourself near to the one closest to the Imam. Take note, too, that a saf must start from the middle part, which is the closest to the Imam.
 
Peace Be Unto You
Assalaamu’alaikumwrwb