how to combine the latest key and the previous key value

Question

hi....after i finish my combination, i need to combine back my values to the lastest key.
For example:
my previous data set 
1 2 :3
1 2 3 :4
1 2 3 4 :1
2 3 :2
3 4 :1
......
after i doing the intersection(using the key),i need got the new keys.
2 1
2 1 3
2 1 3 4
2 3
3 4

Now, i need to take back the previous values from the previous data set and combine with the lastest key
the expected result that i want is like this:
2 1 :3
2 1 3 :4
2 1 3 4 :1
2 3 :2
3 4 :1

the values is come from previous data without changing anything.
how i combine this two so that can show this result?