I've been learning to play the Cuban Tres, or Tres Cubano, since 2015, after first hearing one on Son De La Frontera recordings.

The Cuban Tres (Spanish for 3) has 3 pairs of strings on it either tuned in octaves or, in the case of the middle set, tuned in unison in a GGCCEE patern.
My first 2 Cuban Tres were 3 quarter sized acoustic guitars restrung in the Tres style.
Since then I've purchased a purpose built Tres.

You can keep up to date with my progress via the Pablo Fanque Facebook page, where i'll be posting recordings and video.