My question involves real estate located in the State of: PA

Keep in mind that we must assume that there was never any formal easement in writing or recorded relative to this situation until research proves otherwise. Working from this perspective, here is the situation. Property A includes a driveway and a house. Property B, next door, includes only a house. Property B does not have a driveway and has enjoyed the use of the driveway on Property A. Property B was purchased 15 years ago and the new and current owner is the brother to the owner of Property A. The PRIOR owner of Property B, who was not related to the owner of Property A, enjoyed use of the driveway to access his property. For sake of the of argument, as this fact is not known, we will assume that the right to use the driveway was without conflict for all of those years, which exceed the 21 years, which seems to be the "magic number". Again, if there was any formal easement between the former property owner and the owner of Property A, it was never memorialized to the new owner's knowledge. It was, at the very least, never recorded. Now, the two property owners, unfortunately, are at odds and the owner of the driveway, (Property A) is planning on fencing off the driveway to keep his brother off of it and, effectively, eliminating all means of access to his house. Assuming that access to Property B, for all previous owners, has been permitted by the owner of Property A by an informal "handshake", where does that leave the current owner, from a legal perspective?