I ordered size M (5-6) because other reviewers suggested they fit the small. Now my daughter is a size 4 and these shirts fit like a 5 or 6. I think if her brother is a size 4 they will fit him like a 5 as boys clothes appear slightly larger than girls clothes of the same size. Size. The shirts are really good, especially for the price. I am very happy with my purchase.
The Good Day Lab Clean Shield: Ultimate Comfort and Breathability in Tagless 4-Way Stretch Polo
43 Review
Boys' Long-Sleeve Disney Star Wars Marvel T-Shirts by Spotted Zebra
46 Review
Kid Nation Kids' Tagless Long Sleeve V π Neck T-Shirts 4-12 Years - 2 Packs and 3 Packs
45 Review
Soft Brushed Fleece Crewneck Sweatshirt for π Boys and Girls 4-12 Years - Kid Nation Kids
42 Review
Funny Guy Mugs Tearaway Sweatpants: Playful Boys' Clothing for Fun and Active Days
49 Review
π₯ Stay Warm and Active with Rocky Fleece Thermal Underwear Bottoms for Boys
44 Review
π Fruit of the Loom 6 Pair Cushion Ankle Boys' Clothing: Comfy and Stylish Selection for Active Boys
57 Review
Boys' Adidas Active Sports Tricot Athletic Clothing
45 Review