Cannot create a relationship : ambiguity error

Hi

I have few tables. 

table 1

id  abc def

table 2 

id  cid  fef

table 3 

id  cid  sdw

Now table 1 as unique values for "id" and it is connected to table 2 with id. 

Table 3 and Table 2 cannot be connected as it does not have unique values for id. So I merged column 'id' and 'cid' in both table2 and table 3 to create a unique column. 

Now when I try to create a relationship between table 2 and table 3. It shows me an error saying that if I make this relationship active it will introduce ambuigty between table 3 and table 1. So I need to decativate or delete rel bw 3 and 1 in order to make it active. 

But for me relationship between table 1 and table 3 is required as well. What should I do to make both of them active?