Yes, 13th Sky is definitely a goth band because most of their albums belong to the Gothic Rock and Deathrock genres, which are among the core subgenres of goth music. Albums like The Marching Fire, The Sin Sessions, and Frontline are examples of their goth sound.
13th Sky is located in United States, California, Los Angeles, active in 1999 — present. You can find more information about 13th Sky on their GothDB band page.
Want to check if another band is goth? Search other bands.