A member of Pembrokeshire Harriers and then Cardiff Amateur Athletic Club, Omoregie took part in athletics from a young age and focused on the combined track and field events. Born in Durham, England, both his parents emigrated from Nigeria at age twenty. In 2011 his father died of cancer shortly after his sister had died in a car crash. Omoregie focused on athletics and his schoolwork as a tribute to them and received five A stars in his GCSEs that year. He was the Welsh youth champion in the pentathlon in 2012 then won the English indoor junior championship in the men's heptathlon in 2013. That year he began to focus more on his best event – sprint hurdling. At the 2013 European Athletics Junior Championships he set a best of 13.45 seconds for the junior 110 m hurdles in qualifying before placing fifth in the final. He was Welsh junior champion in the hurdles and also runner-up at the English junior championship.