SQL> create table t ( dfrom date, dto date );

Table created.

SQL>
SQL> insert into t values ( date '2014-06-10', date '2018-06-10' );

1 row created.

SQL>
SQL> select add_months(dfrom,12*(rownum-1))
  2  from t
  3  connect by add_months(dfrom,12*(rownum-1)) <= dto;

ADD_MONTH
---------
10-JUN-14
10-JUN-15
10-JUN-16
10-JUN-17
10-JUN-18

5 rows selected.

SQL> select
  2    add_months(dfrom,12*(rownum-1)),
  3    add_months(dfrom,12*rownum)
  4  from t
  5  connect by add_months(dfrom,12*(rownum-1)) < dto;

ADD_MONTH ADD_MONTH
--------- ---------
10-JUN-14 10-JUN-15
10-JUN-15 10-JUN-16
10-JUN-16 10-JUN-17
10-JUN-17 10-JUN-18