The district practice for related contacts who are brother/sister etc will be to use the relationship = Sibling.
To enter related contacts after a registration go to Student TT > Select the student > Contacts ST > Related Contacts SST.
Add a record for each related contact and set the type to sibling.
Go to the next student and add the contacts again.
For each sibling there needs to be two records on the final list for all siblings. A to B and B to A.
For example if there were three brothers, Marvin, Branlon, and Jarrod at the end of the process each brother would have four records on their related contacts SST.
If you were connecting the related contacts for the first time and starting with Jarrod you would enter a record for Marvin as a Sibling and Branlon as a Sibling. There will be two records on Jarrod’s related contacts.
Navigate to Marvin and you will see one record showing a relationship between Marvin and Jarrod.
Next enter Jarrod as a Sibling to Marvin, and Branlon as a Sibling to Marvin.
Navigate to Branlon you will see two records. Enter Marvin as a sibling to Branlon and Jarrod as a sibling to Branlon.
Now each student should have four records on the Related Contacts SST if you look at them all. If you look at their Details SST you will see that each has two siblings.