I just created Hengelhaupt-12. I wanted to add her as a sister to Hengelhaupt-11. I went to 11 and tried to add 12, but the search function would not bring up 12, even with exact birth dates. I then went to 12 and tried to add 11, again with exact information, but no matches were found. So I went back to 12, and created a new sibling, Hengelhaupt-13, because no matches were found by Wikitree. I then merged 13 with 11.
But I am very concerned now because there are only 12 Hengelhaupts on the entire site and search couldn't bring up a sibling even with exact birth and death dates.