login.c has code


        /* If we can't find a pre-existing entry by pid, try by line.
           BSD network daemons may rely on this. (anonymous) */
        if (utp == NULL) {
             setutent();
             ut.ut_type = LOGIN_PROCESS;
             strncpy(ut.ut_id, tty_number, sizeof(ut.ut_id));
             strncpy(ut.ut_line, tty_name, sizeof(ut.ut_line));
             utp = getutid(&ut);
        }
        
The problem is getutid will seatch for entries with the matching
ut_id. However, it uses tty_number to match the ut_id. As the
result, if the second remote login will match the "1" entry in
/etc/inittab:

1:2345:respawn:/sbin/mingetty tty1

You can see that by logging on console and rlogin twice to the same
machine. You won't see the user on console with

# who

The fix is to use getutline instead of getutid.