I took one of your photos and used software to oversharpen the picture.
I wanted to see where the point of focus was located.
As you can see the point of focus is just about center and quickly goes out of focus as you leave the center. With the left and right being way out of focus. The entire hedge behind the subjects should look like the hedge right behind the man's head.
Your new pictures don't show the problem as well because you don't have a close object (like the hedge) right behind the subject(s).
I have to agree with others that have said the lens is faulty.
It your older photos don't show this fault, it usually means that the lens has taken a hard blow or the camera has been dropped. Something has likely dislodged one of the elements in the lens.
It is time to phone Canon Service and see if they can give you a guestimate as to the cost for repairs. Have the camera serial number handy as he will likely ask for it. First, check the date of purchase.
A new camera has a one year warranty by Canon.
That may or may not make a difference in your case.