If they have the same area code and prefix, there is no security threat. The ones that don't have logic built in not to replicate the number called are pretty dumb since that is pretty much a dead giveaway, when it is a known number it is a random coincidence.

If not, then you would have to wonder how they got the number, worst case phone has a virus or their google/apple address book has been hacked. Pretty unlikely though, in these situations simple is usually the truth, which would be coincidence.