Answer:

littermate

Answer	Crossword Clue
LITTERMATE	Pup, to a sibling, e.g.
LITTERMATE	Any in a group of puppies
LITTERMATE	One puppy to another

LITTERMATE	Almost every puppy has one
LITTERMATE	The one puppy that can read?

Crossword

a puzzle consisting of a grid of squares and blanks into which words crossing vertically and horizontally are written according to clues.