After a Membership has been purchased/submitted, you are unable to remove the primary or purchasing Constituent from the Membership Transaction. If you need to make a change who owns the membership, you will need to re-process/re-submit the Membership with the desired edits and then delete the original transaction.
However for the sub-members you are able to unlink them. If you go into the Membership owners Constituent record and navigate to their Memberships tab you will see on the grid a list of sub-members. Each row will have a broken link icon. Clicking that Icon will remove that sub-member from this membership. You can also go into each of the sub-member's Constituent records and on their Membership tab you will also find an unlink icon.