Is it possible to make two TextLabels copy the text of a TextLabel parent?

It is possible. All we need to do is set the child's text as the parent's text, like this:

Child.Text = Parent.Text

In your case, I think it's supposed to be like this:

Insert a LocalScript into the Amount

local Amount = script.Parent

-- // Since your outline's name are the same, we're gonna use a for loop

for i,v in pairs(Amount:GetChildren()) do
	if v:IsA("TextLabel") and v.Name == "outline" then
		v.Text = Amount.Text
	end
end

I'm not sure what exactly you're trying to make, but this code is just an idea of how it's gonna work.