I am afraid any suggestion is not going to make much difference because we can't see the actual image. This are all low res files with very few pixels defining the critical sharpness targets...the eyes. There is little data to work with. Are these crops of a larger image? Without light on the subject(almost all are backlit) pulling detail out of shadows is not effective. In backlit situation use fill flash, preferably off camera BL mode, for subject fill in a backlit scene. I see nothing wrong with the focus, just too little data defining the most important subject, the eyes. A portrait can be pretty blurry and our perception is of sharpness if the eyes are detailed and sharp. In fact, overly detail portraits are not desired in most cases but if the eyes are not well defined and illuminated, nothing looks sharp in portraiture.
The backgrounds in most of them are distracting and perspective distorts his proportions. Try getting down on his level to shot towards him, not down on him, in fact, for most realistic proportions and body look, shoot parallel to the ground about his waist high. Fill up more of the frame with him, so more pixels define his face if you want the appearance of sharpness, and get some light on his eyes. You can do that with a reflector in backlit situations or just turn him around so the light direction fills his face. Shadows are the enemy of detail, just as high ISO is. Adding fill flash allows shooting at lower shutter speeds since the flash is much shorter duration than your fastest shutter speed, so it helps to freeze the subject. If ambient light it too great to freeze motion, stop down to lower ambient contribution to the exposure, so the ratio of flash to ambient increases. Avoid using the popup flash in situations where the flash is the primary light source, or else you will get the dreaded "flash look" that flash almost on axis of the lens produces. In strong backlit cases, the popup should work fine for fill which brings out all the detail in the face and gives the impression of sharpness.
Can you post full-size JPGs, straight out of camera so we can see really what was captured? If you have an FTP server or some way to post the full-size file we can download, we can tell you really what is going on. Now we are just guessing.
