When relatives are "twice removed" from each other, it means that they are two generations separated from one other. Cousins can be once remove, twice removed or any other number of times removed.
If two brothers each have a son, one named Joe and the other named Charles, Joe and Charles are first cousins. Charles' son and Joe are first cousins once removed and Charles' grandson and Joe are first cousins twice removed.
If Joe has a son named Jimmy, Charles' son and Jimmy are second cousins, and Charles' grandson and Jimmy are second cousins, once removed.