Relationships

First -- go to your Profile
Click Edit
Click "Relationships" at top
Then, under "Remove" - if there is a white box across from the relationship to your ex- click it,
Then click 'Save & Close'
If you can do all that, you should be done

If not - then
A Curator can do that
Post the request in https://www.geni.com/discussions/257430
Include - if it is true - that there are no children of the two of you
Include he is still connected as your ex- in Tree View and you do not want even that connection
Include you tried doing it yourself but you are a Basic User and [where it failed / what you could not do]

(Some Curators are more familiar and willing to do than others - patiently respond if you get response you can do it yourself or etc)

Job Waterreus -- Relationship Path goes thru ex-partner as if it was Partner -- and from what I have seen, Geni's determination of who is in your Max Family treats your ex-partner the same as partner -- so you get birthday notices of relatives of ex-partner and can see and edit their profiles, and ex-pzrtners family can see and edit your family, etc.
Hiding does not help prevent any of that.