Formula to remove smaller text string in cell

Hi. I am having trouble working with a list of names, specifically first names that sometimes contain middle initials and other times do not. Here is an example of the data found in the Fname column:

Mike
Chris S.
Tom R
S
M
Roger
L
Quin T.

What I need to do is remove the middle name initials that occur randomly throughout the list but also keep the occasional cell which only has a first name initial (like the: S M and L in the example). Once the formula is ran the example data would look like this:

Mike
Chris
Tom
S
M
Roger
L
Quin

So it removed the smaller text string in the cell but kept initials that were alone. Any thoughts I am having some trouble with this one.

Thank you both so much! This is going to be an enormous help and will save me personally a lot of time. Thanks!