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to carry (a child) on one's back; to piggyback
母が幼い妹をおぶって歩いていた。
Mother was walking with my little sister on her back.
母は泣いている弟をおぶった。
Mom carried her crying little brother on her back.
父が子どもをおぶって歩いている。
Dad is walking with his child on his back.