"From where are they bringing their books? _______ bringing _______ books from ________"
The words that best fill the blanks in the above sentence are
They're bringing their books from there.
They- used for specifying 3rd person object eg, 1) They were surprised with gifts.
Their- used to specify any object in relation with the 3rd person. eg- 1) Their cycle was repaired, 2) we eat ours and you eat theirs.