The difference, by the numbers
They have no ingredient in common: the Lemon, Lime and Bitters has lime juice, lemon-lime soda and alcohol-free aromatic bitters, the Shirley Temple grenadine, lemon juice and ginger ale. In parts, a Lemon, Lime and Bitters is 1 lime and 10 lemon-lime soda; a Shirley Temple is 1 grenadine, 1¼ lemon and 22 ginger ale. By volume, the Lemon, Lime and Bitters is 91% mixer and juice and 9% citrus; the Shirley Temple is 90% mixer and juice, 6% citrus and 4% syrup and sugar. Different bottles, similar balance: that makes them close cousins on the ratio map.
They are about equally strong in the glass (both 0.0% ABV), and they hold about the same alcohol (0.00 standard drinks each). The Shirley Temple has more calories (about 86 against 68) and more sugar (19.9 g against 16.5 g). Both are built and served in a highball.