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In general, adult female characters have hips as wide as their shoulders, whereas male characters have shoulders that are much wider than their hips. Guys tend to be more angular than girls, who have soft curves as opposed to sharp angles. You can express this in the arms, elbows, legs, hands, knees, feet, and ankles. Male neck muscles tend to ride up higher on the neck than female neck muscles, and they have more pronounced shoulder muscles.
Children are pretty androgynous in regards to basic body shape until they hit puberty.