Okay, psychoanalytical tends to focus on early development as a source for any problems and see’s repressed unconscious desires, delays in the early psychosexual development stages [ie. anal, oral etc.] as reasons for maladaptive behaviour. They do not view it as biological, instead of looking for an underlying medical cause they focus on recovering unconscious reasons as to why a person has developed a disorder. Considering what we know about the biological underpinnings of psychopathology very, very few people would subscribe to this approach and psychoanalysis in general has fallen out of favour with the psychological community.

Behaviourism operates under the belief that all behaviour, including maladaptive abnormal behaviour, is learned. This can be through learned associations, reinforcement of behaviour, or modelling our behaviour on others. It also believes that these behaviours can be ‘unlearned’. It’s actually quite an effective approach in terms of treating phobia’s, addictions and psychosexual disorders - which do involve associative learning a lot of the time. However, it doesn’t really address or prove to be an effective approach in other areas of psychopathology.

Yes, there is such a thing as depression with psychotic symptoms, as well as schizoaffective disorder which is characterised by psychotic symptoms with major mood disturbances.  I would talk to your psychiatrist about this, they may need to change your dose or reassess your diagnosis if they are unaware of the psychosis [although I’m assuming if you’re on an antipsychotic they are aware]. Antipsychotic’s should be controlling the psychotic symptoms, so the fact that you are experiencing them while on this drug means that a different antipsychotic may be of more benefit.

A feeling/attraction/thought in itself is not wrong. A behaviour that can hurt someone is wrong. So the fact that you are in love with your brother is not necessarily wrong, or at least to me - from a moral stand point. I think that things like this can happen, if you’re close to someone, if you love someone, if you grow up with someone, then there is a chance you will grow attracted to them in some way. It is not indicative of a mental illness, although incestuous relationships are clearly frowned upon in most societies, but one attraction [I’m assuming that by ‘in love’ you mean that you are sexually attracted to him, as having affection and love for your brother in any other sense is expected] does not necessarily mean you are mentally ill.