I understand that Justin Timberlake’s voice is geared to sing high notes. Sometimes I hear it tremble but it sounds good. When I go back to singing his way should I copy the trembling?
I don’t recommend copying anyone — I think it is most wonderful and wisest to find your own, unique sound. However, vibrato (trembling as you say) is a natural component of a healthy vocal sound and generally improves the quality and beauty of the voice so it is a good thing.