Problem - Webi merging a variable with a dimension

Hi All,
 
I'am new here and also a newbie in Webi.
 
I need to merge a variable with a dimension. After some research, i found, it is not possible. may be you have an idee how can resolve my problem:
 
I have 2 queries :
 
Query1:
Person, Parent, HouseId
 
A    A    1
B    A    2
C    B    Null
 
 
Query2:
HouseId, Number, Street
 
1    11   s1
2    22   s2
 
 
I want to build one report (HouseId, Number and Street for a Person, if the person has no House get the one of the Parent):
 
Person, Parent, HouseId         Number,   Street
A    A    1                                  11        s1
B    A    2                                   22       s2
C    B    2(HouseId from parent B) 22       s2
 
I merged the diemsnions HouseId from the queries but still only have data if the HouseId is not null.
 
So I created a new Variable

and it works for HouseId.
 
But i can't get the Number and Street for the Person C.
 
 
Thank you for any suggestion