SQL & PL/SQL

I need SQL(for hierarchical tree) for a function which accepts node as input parameter and returns ref cursor.

Following is a sample tree:

1
--2.1
----3.1
------4.1
--------5.1
----------6.1
----------6.2
----3.2
------4.2
--------5.2
--2.2
----3.2
------4.2
--------5.2
----3.3
----3.4
------4.1
--------5.1
----------6.1
----------6.2

1 is at the root level and 2.1 & 2.2 are immediate children and so on.
The output tree should be all related parents and children of the passed node.

e.g:

If the input is 4.1, the output tree will be:
1
--2.1
----3.1
------4.1
--------5.1
----------6.1
----------6.2
--2.2
----3.4
------4.1
--------5.1
----------6.1
----------6.2

If the input is 4.2, the output tree will be:
1
--2.1
----3.2
------4.2
--------5.2
--2.2
----3.2
------4.2
--------5.2

The complex part, I guess, is to remove unwanted(not related) branches from the tree.

Following is the representation of the table RELATIONSHIP

ID PARENT CHILD
1-------1-------2.1
2-------1-------2.2
3-------2.1-----3.1
4-------2.1-----3.2
5-------2.2-----3.2
6-------2.2-----3.3
7-------2.2-----3.4
8-------3.1-----4.1
9-------3.2-----4.2
10------3.4-----4.1
11------4.1-----5.1
12------4.2-----5.2
13------5.1-----6.1
14------5.1-----6.2

Pls. help me out to form this CONNECT BY PRIOR query.

Thanks in advance.