Frank, the half-sister is what we call a "ghost" that occasionally remains after a merge. It is a bug that has been known for several years. You will notice that if you click the link to the half-sister, it will take you back to the same profile - this is what is called an "auto-redirect" that happens to all links to profiles that have been merged away.
To fix it, all you have to do is go to the father's profile, edit it, and remove the half sister as his child.
On another note, Francis-5589 should not have been merged into Francis-5888. The merge should have gone the other way. We ALWAYS merge into the lowest number when the LNABs are the same. I don't understand how this could have happened - the system should not have permitted it.