We have contracts with June and August use years at OKW.
Keep in mind you can't combine the points for a single reservation. So your 230 and 100 points would be spent separately from each other. If necessary MS will use the points separately and then link the reservations so you don't actually move during your trip.
Also, you cannot split points for a single day. For example a villa costs 27 points for a night. You couldn't use 14 points from one contract and 13 points from the other.
Just for example, say you want 5-nights at 27 pts/night for 135 points total. You couldn't use your 100 Sep points and 35 Aug points for this ressie. You could use 81 Sep points and 54 Aug points though to reserve 3-days and 2-days respectively, and link the reservations.
The easy solution is to just transfer the points from one account to the other. Transfer your 100 Sep points to your Aug year and then all 330 points are treated as one group. Just be aware of the limits on transfers. For example you could not transfer out of Sep into August some of the points, and then later transfer points from August back into Sep.
We have the exact proportions you have, 230 points and 100 points. What we generally do is bank and borrow from each contract separately. For example use the 230 pt contract this year and bank the 100 pt contract. The next year maybe borrow the 100 point contract (to give us up to 300 points available) and bank the 230 point contract. ETC. With banking and borrowing we never really wind up having to use both contracts to make a single reservation. (Although have had to transfer a few points a few times)
Just keep in mind that your two contracts are just as separate from each other as if you yourself owned a 230 point VWL contract and your brother/sister owned a 100 point VWL contract.
Hope this helps.