1st one
your background exposure is pretty good however the 2 people need some fill light either use a reflector or some flash through a shoot through umbrella make sure the flash is balanced to the background to keep it nice and subtle
also the composition is too centered it looks like the couple are dropping out of the frame this could be fixed by moving the shot up so their heads are on the upper rule of thirds line
too much back is showing and both are profile shot
nice idea with them watching the sunset however a better way to pose would be have one person back to camera the other lying across but facing toward the camera more and looking at the other person, say have the guy in a similar pose to the one he is in and the girl with her body and legs behind him leaning on her right arm looking towards him, that way with him looking at her too they will both be engaging the camera more and
colours are a bit washed out too
the second pic is also off compositionally, the girls head looks disembodied and is dropping off the bottom of the shot the guy is on the right edge looking off out of the shot. a general rule is if the person is looking in a direction you want some negative space in that direction or a subject
neither subject are engaging the camera or the shot
also the colour / wight balance is really washed out
are these jpgs shot with adobe rgb in camera instead of S-RGB?
hope that helps, have a look at some basic composition guides, its ok to break the general rules of composition but you have to know what they are and why you are breaking them too. but generally if you follow those rules you will always get decent pics
