MyMemberPage.php

class MyMemberPage extends \Page
{
    private static $table_name = 'MyMemberPage';
    private static $controller_name = MyMemberPageController::class;
}

MyMemberPageController.php

use SilverStripe\Control\HTTPRequest;
use SilverStripe\Security\Security;

class MyMemberPageController extends \PageController 
{
 // This is where you tell the controller what actions it can perform.  Each would be in the URL (eg. /memberpage/delete)
  private static $allowed_actions = [
    'save',
    'delete',
    'confirm'
  ];
        public function delete(HTTPRequest $request)
        {
            $accountId = $request->getVar('account');
            $account = Accounts::get()->byID($accountId);
            if ($account->AccountOwnerID === Security::getCurrentUser()->ID) {
                //You can delete the account here
            }

        }

        public function getAccounts()
        {
            return Security::getCurrentUser()->Accounts();
        }
}