When I summon a baby frostbite (using /summon minecraft:frostbite -11.50 101.00 61.43 {Age:-13432,AgeLocked:1,IsBaby:1, NoAI:1}) or via using a frostbite egg on an adult frostbite (which is also NoAI if it matters), it is invisible.
MC-312719
Baby frostbites are (or can be) invisible
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Oh, if I summon without the NoAI:1 setting, the baby exists and moves, but is still invisible.