Archie is 9 years old and wears size 8-9Y
Nico is 4 years old and wears size 405Y

Garment measurements by size (approximately):
Size (cm) 18-24 2-3Y 4-5Y 6-7Y 8-9Y
Waist 20 21 22 24 25.5
Length 24.5 26.5 30.5 34 36