The only bug I can find on the issue is this one. Have a look at the comments, it was closed as won't fix. It looks like the family picking behavior has changed slightly between 0.99.7 and 0.99.8, but it has gone from potentially unstable behavior to the correct, stable behavior. So if your application's family picking was broken, it means you were previously relying on functionality that could've crashed, and it's necessary that you fix it. Davo's comment explains what the difference is, and it seems to only affect events with Create Object actions. So if you know the way it now works, you should be able to inspect all your object creating events and check they are set up correctly.
I know it's kind of annoying but the engine has always worked this way - the real bug was that 0.99.7 let you get away with it - but hopefully this is one of the last pre-1.0 pains.
Let me know if anything else has changed with family picking (but I doubt it, since we haven't changed any of that code for some time).