Not sure what you are trying to do - a more meaningful description of the problem would help.
Whether you need to insert a missing generation into an existing line, or wish to remove an existing generation and then re-link what were the parents and children, the solution is similar.
In edit mode, go to family view and click to edit the person concerned. Scroll down and you will see where the parents are listed. You can then remove those parents or change them to someone else already in your tree.
Do this for the, presumably, two individuals that require fixing and the generational linkages should work out correctly.
Regards,
Ian Marr