But remember that 5 in one cabin can be rather cramped and you do only have one bathroom...
If one child can go in a cot the answer is yes possibly - otherwise all lines i know of do not give details for a fifth person - so no. some companies do family suites though. call a cruise agent ie the number above - freephone 08000911629 !!!!!!!
Some of the newer Royal Caribbean Ships (Freedom, Liberty Independence, Oasis etc) do have family cabins which will accomodate 5 to 8 depending on which one you chose and they range from insides to outsides to suites.