If Justin said that he was 7 years old (in Europaian years) then he was 24 Earth days old (1 Europaian year is 85 hours). So he was born February 1st 2019, therefore he’s 3 Earth years now.
Hmm, good thinking... I thought that despite he looks young, I think that he may be at least already many years old but it actually depends on the planet hours. Good theory btw!