Hello Kanchan - I have tried to simulate your data. Here Table A to Table B is having 1: N relationship and Table A and Table C is having 1:1 relationship.
Once I bring the data in Tableau, then it look like the following.
and the output is also expected
1 to N.twbx 18.1 KB
I don't know about the data structure. I guess you've to check your joining conditions of second join. It will be more helpful for us if you share some sample data from each tables.