People will probably always say things like this, particularly if you are young and, as a consequence of working for your father, relatively well off, I know a few people who are in a similar position and I have been in a similar place myself as an intern. Don't worry about it, if they are your friends out side of the company they will get bored of it eventually, if they are your co-workers put in your time and do your bit of the work, don't be standoffish and they will come around. If your father is doing well he is probably good at what he does, and thus wouldn't give you any responsibilities if he didn't think you were up to them, you will prove this to others with time. Make sure you work well enough that there is no justification for any of the accusations and keep cool about the whole thing, it will pass.