I have booked and apartment and the owner is asking me for a lot of data such as passport number for every person in the group.

Is this normal? 

The owner is required by law to supply a lot of data about each guest to the police.

If the owner does not require this information it probably means that it is not an official accommodation. 

If you are llucky the owner will be using an app which makes it easy to send the data.

This is quite normal in Spain. 

You eevn have to show your passport when you visit monuments.