Yes, when you move the two records, they will become one, so there will only be one person connected to the parents. They will be ‘losing’ a brother but it will then be correct. Lol
Merge should always be done to the lower number. When you are doing the merge, you can change anything, other than the last name at birth. When you have completed the merge, you can change the last name at birth, if needed, as long as your were a PM on one of the records.
If 2 records are merged that had different PM, all PM will be associated to the new merged record.
Make sure to edit the biography during or after the merge to clean it up since all the bio text will be copied from both into the merged record, frequently duplicating information.
Hope this helps.