How to find which child has less than 3 child from my hierarchy of 1x3 matrix using single mySql query

Question

I am using 1x3 matrix to store data in mysql like below:-

ID parentID directID

1. 1 0 0 <- This is first ID (So parent is no one),
2. 2 1 1
3. 3 1 1
4. 4 - 3
5. 5 - 4
6. 6 1 1
7. 7 2 1
8. 8 2 1
9. 9 2 1

10. 10 6 1

11. 11 6 2

I am working on a MLM (multi level marketing) project with 1x3 matrix plan.

As I am using 1x3 matrix structure, I have to find the child which doesnot has 3 child below it, given the top ID as 1 (1 is directID of new ID under which it has joined). The New ID that joins the team has to assign a parentID.