In a Web form I have a question to which an answer needs to exist, so that a result can be shown to the user. It's about the users family status (single, family). 
Because there is a majority of users that prefer the first option "single" we decided to prepopulate that option. 

Should this still be marked as a mandatory field (\*), though the user does not have to interact with it in order to provide the information? The general question that arises is if a mandatory field is a field that the user (possibly) needs to interact with or if a mandatory field is a field that is required by the software in order to do its job? Does anyone maybe know some research about the users' expectations and mental models?