I'm not a portriat shooter so I don't know what modelling lights are, but the light here from the flash is way too bright and leaving harsh shadows on the boy on the right's face. Depending on the brightness of the modelling lights could you just use them instead of flash? A light on the left side, as high as it can go, tilted down, and a light on the right, at face level as fill light would give soft, even lighting. The poses are really cute and they look like naturals!
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