如果sth是名词,则两种句式都可以：give sb sth = give sth to sb.
但如果sth是代词（it、them等）那就只能用 give sth to sb.就是把代词放到中间.这有点像动词短语接宾语,宾语是名词,可以放在中间也可以放在后面,但如果是代词,就只能放在短语中间.如：pick up the flower= pick the flower up.
pick it up.不能说pick up it.个人看法.