Create a Relationship Error

Thanks for az38's concern about this issue.

Hi, guybrit 

I am glad to help you. 

According to the problem you described, first you need to connect Power BI to different data source and then open Power Query Editor:

Select one of the tables and click Append Queries as New, then select the corresponding two tables and you will get a new table:

Ctrl+click Base Points and Bonus Points, right click and select Replace value, replace null with 0:

Close&Reply.

New measure in the new table:

Total Points(Base + Bonus) =
SUMX ( AppendTable, AppendTable[Base Points] + AppendTable[Bonus Points] )

I hope my suggestions give you good ideas, if you have any more questions, please clarify in a follow-up reply.
Best Regards,
Fen Ling,
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