Gary Mitchell and James Tiberius Kirk were childhood friends who met when the Kirk family lived in Iowa. Well, okay, that's my ''canon'' in STSOP.
Point is, there're enough ''empty years'' to explore a great many of the characters without always thinking ''alternate timelines'' and so forth.
Of course, in my case, while I give the most weight to the material from the original TV series, I also don't purposely tread on anything unless absolutely necessary. I just won't trade storytelling to align forty years of screen franchise.