[EDIT: These first two paragraphs were in response to OP's original post asking about sharing points and using points at different times of the year. You guys gave OP so much great feedback so quickly, some of this looks out of context!]
Yes. One of the keys to
DVC is that you are not buying a specific type of accommodation for a particular time slot, like traditional timeshares. You buy (or more accurately lease) points, which you can then spend any way you choose.
You receive a certain number of points each year for the length of the contract. Saratoga Springs contracts expire in 2054; all other DVC contracts expire in 2042. If you do not plan to use all of your points in one year, you can bank them forward into the next year - subject to some restrictions. If you need more points one year, you can borrow from the following year - again, subject to some restrictions.
Multiple owners:
Our family did exactly what you are contemplating. We bought a 310 point OKW contract resale, and are in the process of adding on a 120 point SSR contract. That should be plenty of points for our three families, because we all live in Miami and tend to just drive up for 3-5 day stays, rather than longer trips.
The only caution I would give you about doing a combined account like that is to make darn sure all of the people involved fully understand the applicable rules, regulations, restrictions, etc. of DVC. They are certainly not onerous, but if someone doesn't understand what they are doing, they could put all of the owners in a position where the use of everybody's points is restricted.
You'll also have to keep track of who uses what, and how many points each group has available when, how many they've borrowed/banked, etc. You can do that with a pad and pencil, or Excel. Point management guru Caskbill is working on a tracking software package now which will also make tracking a lot easier.