Agree with all the above.
You probably should ask your BGO if the parents should be there for the interview (when you are scheduling the interview). This will clue you in on how that BGO wants to run things. I would expect almost all BGOs will say "yes" and then tell you how it will be ran --- something along the lines of --- that the first 15-30 mins will be together and then the rest of the time is one-on-one. Most BGOs know how to handle this, even if you or your parents aren't aware when the interview is being conducted, by politely asking, that the next portion of the interview is between the candidate and BGO only.
I encourage parents/guardians to be there, but sometimes it is hard to get both (work schedules) or even any (college students) -- parents ARE NOT REQUIRED to be there, but it is a "nice to have" so they fully understand everything, as well. So do not fret if only one parent can make it (one is better than none) or, in some cases, none.