have tried multiple times with different harems, not always work.
In some cases the option to propose a certain harem doesn't even show after proposing to someone else of the harem.
In some cases i proposed to both or more parties in different places and some of them weren't included in the wedding like if i hadn't asked them.
The only 100% success i have had with the harems is when i propose to all of them at the same time.