May I know why there are 2 external ID for the same Facebook account?
Please note each Facebook page will have its unique PSID for each Facebook user, there will be multiple external ID for the same Facebook user if you have connected to more than 1 Facebook channel (i.e. the same Facebook user will have 3 PSID if you have connected to 3 Facebook pages)
You could use the channel filter to select the channel and get the correct members in the member page.