teen/cub
If meaning teenager (adolescent) on a (younger) cub, use instead: Adolescent, adolescent_on_younger, young_<form> (young_anthro/young_feral/young_humanoid/young_taur), younger_form.
If both are teenagers, then use Adolescent, young_<form>.
If meaning a teen cub, use instead: Adolescent, young_<form>.