select
	/*+ qb_name(main) */
	gp.small_vc_gp,
	par.small_vc_p,
	chi.small_vc_c
from
	grandparent	gp
left outer join 
	parent		par
on	par.id_gp = gp.id
left outer join 
	child		chi
on	chi.id_p = par.id  -- to first table
and	chi.id_gp = gp.id  -- to second table
;

--------------------------------------------------------------------
| Id  | Operation            | Name        | Rows  | Bytes | Cost  |
--------------------------------------------------------------------
|   0 | SELECT STATEMENT     |             |  2000 |   115K|   517 |
|*  1 |  HASH JOIN OUTER     |             |  2000 |   115K|   517 |
|   2 |   VIEW               |             |  2000 | 80000 |   121 |
|*  3 |    HASH JOIN OUTER   |             |  2000 | 68000 |   121 |
|   4 |     TABLE ACCESS FULL| GRANDPARENT |  1000 | 15000 |    40 |
|   5 |     TABLE ACCESS FULL| PARENT      |  2000 | 38000 |    78 |
|   6 |   TABLE ACCESS FULL  | CHILD       | 10000 |   185K|   381 |
--------------------------------------------------------------------

Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------
   1 - SEL$A4DA5D2A
   2 - SEL$58A6D7F6 / from$_subquery$_003@SEL$4
   3 - SEL$58A6D7F6
   4 - SEL$58A6D7F6 / GP@SEL$2
   5 - SEL$58A6D7F6 / PAR@SEL$1
   6 - SEL$A4DA5D2A / CHI@SEL$3

Note the VIEW operator in line 2 of the plan, where the non-mergeable in-line view makes it presence felt.