the Rat (first sign of the Chinese zodiac)
「子」 has other readings with different meanings.
child; kid; teenager; youngster; young (non-adult) person
child (esp. a boy)
干支で今年は子の年だそうですね。
This year is the Year of the Rat.
子は十二支の最初の動物です。
The Rat is the first of the zodiac.
彼は干支で子年生まれだそうです。
He was born in the Year of the Rat.