Multiple Column Key - SSAS Tabular

I have a requirement where most of the tables have a two column relationship with others. For instance,

Table 1 (related to Table 2):

RoundID + EntityID => Primary Key

Table 2:

RoundID + EntityID => Primary Key

Table 1 (also related to Table 3) also has similar relationships with other tables like:

Table 3:

RoundID + ObjectID => Primay Key

In SSAS Tabular, I have calculated columns in all the tables (to combine RoundID with the other KeyID). Table1 has about 8 relationships with 8 other tables with different KeyIDs (RoundID is common to all tables).

Can someone please suggest the best way to handle these relationships without having multiple calculated columns.

Thanks in advance.

Mohamed