But Paul Davis, First of His Name, you cry, that means someone is still buying those ex-Boomer family homes!
Why yes, yes it does. But those retiring boomers, in great numbers and armed with (relative) boatloads of cash, are moving to places that they would not have settled in before reaching this stage of life. 20-30 years ago, their money would have sloshed around inside the places they already lived, as they perhaps needed 1 more or 1 less bedroom. [0]
But now, they are on the move. Bend, Santa Fe, Bellingham, Ithaca ... many, many communities seeing huge influxes of cash buyers that would not have happened before.
I'm sure there are many other forces at work in today's crazy residential real estate market, some of them possibly larger/more important. But I think that this time period, right in the middle of the Boomer retirement wave, is also affected by this too.
Disclaimer: I resemble the above remarks.
[0] EDIT: also, as noted by others here, some of the buyers of those homes are not in any way "other people buying family homes" but investment/financial service corporations.