I was looking through all the Construct Family Groups from 1st Edition with the idea of seeing what might show up in 2nd Edition when I noticed a trend.
There are the expected big family groups: Golems, Clockworks, Robots
And there are some smaller family groups: Automatons, Idols, Poppets
But then I notice two potential construct groups that have never been clearly defined, Sentinels and Guardians
Sentinel
--Sentinel Thassilonian, Bronze Sentinel
--Sentinel Thassilonian, Iron Sentinel
--Sentinel Thassilonian, Ivory Sentinel
--Sentinel Thassilonian, Marble Sentinel
--Sentinel, Sentinel Hut
--Sentinel, Shell Sentinel
--Sentinel, Ship Sentinel
--Sentinel, Smoke Sentinel
Sentinels as a group seem to have a theme where they are tied to a specific site or location and have an innate sense for who are allies versus who are enemies. Sentinels may also actively avoid hitting allies with their attacks or may be able to explicitly exclude allies from being hit by their attacks. The one that breaks this mold the most is the Sentinel Hut, but there is still plenty of potential for Paizo to turn this into a Construct Family Group
Guardians
--Guardian, Angelic Guardian
--Guardian, Gargoyle Guardian
--Guardian, Golden Guardian
--Guardian, Graven Guardian
--Guardian, Guardian Doll
--Guardian, Guardian Scroll
--Guardian, Rune Guardian
--Guardian, Set Guardian
--Guardian, Tattoo Guardian
Guardians as a family group are far less clear in theme. The best I can gather is that a Guardian is tied to a person or specific object whereas a Sentinel is tied to a specific site or location. The best examples are the Angelic Guardian and the Tattoo Guardian where their descriptions clearly assign them to protection of an individual. The rest of them fit this mold loosely at best. If Guardians are constructs that are specifically attached to the protection of an individual or specific object, some Guardians on the list are likely to be re-identified as Sentinels.
Anyway, this is just something I noticed and thought it was interesting.