You can add multiple siblings by adding student as a sibling to each other’s, but you can only add sibling to those students in which no sibling is already added, so to add multiple siblings e.g. A, B, C, D follow these steps-

1. Select student to which you want to add sibling e.g. if you want student B as sibling of student A so select student A profile (note: student A should not have any sibling).
2. Go to student A profile and click on Edit button, then add sibling, student B here and click on Save button.
3. Now, edit student C profile and add student A or student B as sibling here and click on Save button.
4. Same as edit student D profile and add student A or student B or student C as sibling here and click on Save button and so on.