I tend to believe there is more destroying to be done long term by keeping this kind of secrets that by revealing them. But everyone is different and ultimately, it's to you to decide after weighting the pros and the cons.
As Yansusu noted, it's not impossible that it is stolen pictures (it happened to me ten years ago.. I'm sure it's even more common now with the apps etc), which makes it even more important to find out what's going on. I mean, in any case we have a problem here. If it is not your dad, I'm pretty sure he won't be too happy about it either, because you're probably not the only one person he knows in the area to have found that profile.
What I would probably do would be to tell him.. more or less that! That you found something about him on the net that may or may not have been posted by him but needs to be addressed in both cases, etc.
As for your mother... it's very difficult to say anything at this point. If you don't speak to your father about it, it makes it more difficult to speak to your mother, especially not knowing if it's actually him.
If you do speak to your father, then it will depend what he says obviously.. if he says it's him you may want to tell him that's it's going to be difficult to lie to your mother.. but you don't want to make it sound like a threat either.. difficult to be honest but not menacing.. anyway that's only suppositions at this point.
Your first step has to be to decide if you ask your dad for explanations or not. Maybe after doing a bit of research.
There is nothing on the profile that could make you think it's a true or fake profile? Did you search the pictures to see if they show up anywhere else abnormal on the net?
