Maybe boy's hair is slightly out of focus. If so the overall depth of field maybe less than ideal. On the other hand the great grandfather is the principal character and here everything is spot on. No reflection in the glasses and his eyes are great. You can almost feel the texture in his pullover. I bet he is proud of this picture. It's a great portrait.
A wonderful fsmily portratit. As noted by pentaxuser Santiago's hair is ust beginning to lose focus, looks as though he leaned forward after you had composed the shot.
I am no expert on portraiture and critique is a lot easier than achieving the end result but it may be worth moving subjects a little further away from the background, that way you can fet the 'blur' on thre background but may have enough leeway to accomodate such an occurrence.
On the composition and clarity I have to agree with pentaxuser it really is a wonderful shot, let's be honest your grandfather will treasure it because of the composition etc. he will not be overly concerned about a slight loss of focus.
Thanks for sharing; CJB