If you are using 'Wikitree+ Search Results' for the 1st option on the left side, you are not using descendants.
You could select 'Check Watchlist' for that 1st option, so it would check all profiles that you are on Trusted List for.
Have you created all the profiles for the children? You could use creator_Nellis-1011 to check for all profiles you created and have orphaned.
Ancestor generations is limited to 20, Descendant is limited to 5
Do you know what other surnames are involved? You could change the query to check for those surnames also. You can also enter the Nellis-Nelles in the 'Search biography for' box to find profiles that have that in them, but you can't search the entire database for that. You would need to change the 'Profiles to report' option to 'Detailed Report' to see the returned profiles where that search was found. Possibly by initially searching your profile ID with ancestor set to 20 and Descendant set to 5 with All profiles to be included and the search bio box filled in and Detailed Report set, you could find some of the other surnames that would be returned with 'Found' in the Search ? column to indicate that that entry was found in the profiles. Sorting that column, you could see some other surnames, such as Wagner, Nellis, Settle, etc.
I think 'checking your Watchlist' will probably return most of the records that you are looking for, unless you have orphaned many and removed yourself from the Trusted List. You will need to have the 'Profiles to report' option changed to 'Sources report' to see the Sources column in the table before export, but changing the report type will change the table columns without having to re-run the query, I think.