It is possible. All piggies are different and all environments in which they live differ too. For example, one of our boars loves attention and doesn't even mind strangers - the other will still occasionally run and hide from me. He is really only comfortable with my wife and we've had our two for almost two years!
There are a host of other factors but it could just be their personality. I would need to know more (ages, genders, environment etc.) to be really specific. Just remember, piggies are prey animals and their natural instinct is to run and hide. This is not a personal reflection on you as an owner or their feelings toward you, it's just what piggies do in general. There are plenty of posts on here with tips on how to help this process along and things you can do to help your piggies settle. (a recent one was entitled "confused" and I posted some tips there if you want to check it out).
Best of luck
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