How to count one column's values without another column's duplicates affecting it

Hello there! Here are the details about the problem I have:

I want to count the number of values in one column, without another column's duplicates affecting it. 

Example: I have a table with multiple columns. The columns that matter most are "No." (detail number) and "Family". I want to count the number of values in the "Family" column without "No. Values" affecting them. Whenever the "No." column has a value count of more than 1 (in this example - 1282370) - it should count as 1. 

The result would be: the SDB count for 1282370 - 1. Duplicates don't count.

there are other "detail numbers" that can have the same family. Hence, if the count of one detail for the same family is >1 - it should count as 1.

what would be the DAX expression to get these values?