It is hard to say whether you will ever have an issue. The 20 reservation rule was issued in 2008 as one of the steps designed to correct a serious problem that existed at the time. There were many who had essentially gone into the business of renting
DVC who owned large numbers of points, or went into business with others who also owned points. Those owners had two rules at the time that helped them accumulate even a much larger number of points to rent than the ones they owned: (a) they could accept an unlimited number of transfers into their accounts, and (b) they could be named as associate members on an unlimited number of memberships of other owners. Thus, the lack of any limit on the number of rentals, number of transfers in, or the number of associate memberships, resulted in those owners being able to control and rent a huge number of points at one time.
One significant problem the professional renters created was that they tended to use the huge number of points they had to make reservations at 11 months out for rooms in high demand for times in high demand, e.g., making a large number of reservations for BWV standard and boardwalk view studios or BCV studios at Thanksgiving and Christmas time, and then they would advertise those rooms and times for rental on various sites. (This disboards site actually had some of that activity on its rent/trade board before it adopted in 2006 a number of rules applicable to posting on the rent/trade board, which included a rule prohibiting posts offering to rent a reservation already previusly made unless the the vacation time was less than 30 days out from the date of posting).
That professional renter problem resulted in the adoption of three rules. One is the 20 reservation rule, a second was a rule limiting transfers to one per use year (in or out), and a third was limiting any person to no more than four associate memberships. The effect of the adoption of those rules was to greatly reduce, although not necessarily end, the careers of professional renters, and reduced the problems owners had getting regular reservations.
There were actually a number of reports of owners (suspected professional renters) being challenged under the 20-reservation rule after the rule was adopted. However, it has now been many years since I have seen any posts mentioning someone being notified under the 20-reservation rule. Moreover, one cannot even find the 20-reservation rule on the DVC website anymore, raising some question as to whether it still exists, or maybe it is just now mostly ignored by DVC because the problems that existed before are now minimized.
I kept a verbatim copy of the actual rule from the time it was first published, and it states:
Commercial Use Policy. The Disney Vacation Club (DVC) Public Offering Statement makes it clear that DVC memberships are intended for personal vacation use. The Declaration of Condominium and the Membership Agreement for the Resort expressly limits the use of Ownership Interests to personal use and prohibits use for "commercial purposes," - a pattern of rental activity or other occupancy by an Owner that the Board of the Association, in its reasonable discretion, could conclude constitutes a commercial enterprise or activity.
DVC Members may make as many reservations as they desire. However, if, in any 12-month period, a DVC Member desires to make more than 20 reservations, the DVC Member shall be required to establish, to the satisfaction of the Board, that all of the reservations made by the DVC Member in such 12-month period are for the use of accommodations by the DVC Member, the DVC Members family and/or the DVC Members friends (collectively, Personal Use), and not for commercial purposes. If, in any 12-month period in which a DVC Member attempts to make more than 20 reservations but is unable to establish, to the satisfaction of the Board, that all such reservations are for Personal Use and not for commercial purposes, all reservations in excess of the first 20 reservations shall be presumed to be the use of Vacation Accommodations for commercial purposes in violation of the Declaration and the Membership Agreement (the Multiple Reservation Rule).
Enforcement of this policy will be the responsibility of DVC Member Services as follows. For each reservation made by a DVC Member, Member Services shall determine, before confirming the reservation, the number of reservations made by such DVC Member which are occurring or have occurred in any rolling twelve-month period in which the reservation then being made will occur. If, as a result of Member Services review of the DVC Members reservation history, the reservation the DVC Member is then attempting to make violates the Multiple Reservation Rule and the DVC Member has not established, or cannot then establish that all of the DVC Members reservations, including the reservation then being made by the DVC Member, are for Personal Use, DVC Member Services will not honor or confirm the reservation and the DVC Member shall be advised that the reservation violates the Multiple Reservation Rule and the prohibition on use of Vacation Homes for commercial purposes. For reservations canceled for violating this policy, the cancellation shall be deemed to be a cancellation by the DVC Member and the provisions of the Home Resort Rules and Regulations relating to cancellations (including, without limitation, Sections 5(d), 13 and 14) shall apply.
End Quotation
The rule is not a modicum of clarity. Clear is that it is not an absolute ban on making more than 20 reservations in a twelve month period. Unclear is whether by prohibiting the "making" of 20 reservations in a 12 month period, it prohibits having 20 reservations in one year or simply the "making" of (calling to make) 20 reservations which reservations could actually occur in more than one year; likely the former. Also, it may have limitations to a particular membership or particular member, i.e., it may only apply if the same membership number or the same named member makes the 20 reservations, and thus not apply in your situaton where you have four different membership numbers and potentially four different members making the actual reservations (however, when originally passed, the problem it was addressing with professional renters often involved more than one member in league with another). The rule allows the member to defeat any suggestion of "commercial purposes" but that seems a very limited exception since the member apparently must establish that there were no rentals at all in the first 20 reservations made. My personal sense is that for you the issue may never even arise, and if it does and DVC sees that most of your reservations are for family and the rentals are for covering dues, you will likely be determined as not using your ownership for "commercial purposes."