Could a turbofan have two adjacent fans?
Generally, it is more efficient to have one large than two small devices.

The twin fan solution not only needs a gearbox and driveshafts that a single fan solution does without, it also has more intake and nozzle surface area per cross section than the single fan. This will cause more viscous losses and lower efficiency. The only advantage would be if size limitations make a single fan impossible, but in that case it would be more straightforward to have each fan driven by its own core engine.

Famous examples of aircraft which used a single engine and two "fans" would start with the Wright Flyer models, all of which had a single engine drive two propellers via bicycle chains. But the list is short.
The list of opposite designs where two engines would drive a single propeller or fan would probably be longer, and my favourite from this list is the LearFan.

@jwenting correctly reminds me that for completeness a single power plant driving two contra-rotating propellers should also be mentioned. This is indeed the only way on airplanes of one engine driving two propellers, albeit not adjacent, that has seen wider adoption, from the RR Griffon on the Avro Shackleton to the NK-12 of the AN-22, Tu-95 and Tu-114.

Of course, all single-engine helicopters also use this one engine to drive their two propellers …