In the past, I have used the feature in Compose Message to send a message to the descendant of a given profile, and have used it to send a Message to the (Claimed) Family of a given Profile.
Just went there to do one of those - and 1) No drop-down box as I typed the name - even tho it was a name that would trigger the drop-down window in the Search Box (checked!) - 2) When entered the name, did "Search More" - it found the relative I had entered, but when I clicked on it, it simply disappeared, and none of the relevant claimed profiles were added in the list of recipients -- -- 3) Clicking "Family" - despite the fact there are many Claimed Profiles in my Max Family - resulted in nothing happening.
Also - entering recipient straight in the Recipient Box also failed to trigger the drop-down window of choices even tho it should have - again, "Search More" did work (this time, at least, adding the Recipient to the list)