Some experiment about relationship data that Twitter is attempting to infer:

1. Use the Twitter website
2. Visit any user profile using the "Search" text box
3. Go to "Home"
4. Click in tweet input text box
5. Click in "Search" text box

Try this with people you don't interact with regularly, and with people to which you have (or had) a close relation.

For some people, the name of the person will be offered as an autocomplete suggestion in step 4 and 5, even before you have typed the first character (*).

For me, my ex-girlfriend is the only person for which Twitter is displaying this behavior.

Very creepy, because there is not explicit "relationship" field on Twitter, and the relationship is over for more than one year now.

(*) Searches saved using the "Saved Search" functionality are also appearing immediately in step 5, unrelated to the behavior that is discussed here.