Kanervo was born in Tornio in northern Finland and set national age group records from an early age, breaking the national under-11 record for boys' 150 metres in 2003 and the national indoor under-12 record for 60 metres the following year. He competed in both the 110 m hurdles and the 400 m hurdles at the 2009 World Youth Championships in Brixen, Italy, but was eliminated in the early rounds in both events. In 2010 Kanervo's family relocated to Helsinki, and he joined the training group of national hurdles coach Anatoly Mikhailov. Kanervo represented Finland at the inaugural Youth Olympic Games in Singapore in August 2010, winning bronze in boys' 110 m hurdles (91.4 cm) in 13.53 and breaking his own national youth record; he was the first Finn to win a Youth Olympic medal.