Choroba the cycle has Q. Heres a snippet from the data im running the code on:-

__DATA__
child,    Parent,    relation
Q    M6    E
M6    Q    E
M10    Q    E
M28    M6    P
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As you can see in line 1 & 2, its a cycle and hence leading to crashing of code. Because if i remove first/second line , the code is working fine. But I do want these relations also, so thats why I want the tree to stop tracing back once it has reached 'Q' for a particular child and not go beyond that.