 Vlahov declared himself until the early 1930s as a Bulgarian and afterwards as an ethnic Macedonian.However such left-wing Macedonian activists, former members of the BCP and the IMRO (United) never managed to get rid of their strong Bulgarophile sentiments, and thus practically continued to feel themselves as Bulgarians even in Communist Yugoslavia.He was born in Kukush (present-day Greece) and attended the Bulgarian Men's High School of Thessaloniki.