Huey, Dewey and Louie, e.g.
I believe the answer is:
rhymes
(Other definitions for rhymes that I've seen before include "Similarities of word sounds as in verse" , "Nursery . . . . . . are jingles for children" , "Nursery . . . . . . are simple poems for children" , "Nursery . . . . . . are traditional verses for children" , "Terminal sounds are the same in these" .)