I'm debugging a failed board for a humidity sensing extractor fan. RP1 is the humidity sensor. Q1 and Q2 (SOT-23) look like some sort of dual current mirror, but I don't understand this configuration or how it works. (The other side of R4 is connected to one of the output pins of a MC14049 Hex Buffer).
Here's a picture of the part of the board. Ground plane at bottom. Q1 and Q2 bottom centre (marked KZG).
There are no through-holes on the board that I can see. Resistance between bases and ground appears to be infinite.