In the books, Red and her sister sleep huddled together for warmth and comfort.They're social creatures~

Because Red has grown to associate York with family, she sleeps with him whenever she feels the urge.(Which is most of the time huuur) Junior is already firmly filed under chick-status, which makes Tucker family too. (She would prefer it if York would sleep with Tucker, her and Junior and wonders why they sleep in separate rooms at all but is chalking it up to 'humans are weird' for the time being)