I think the way you described the diagnosis of schizophrenia is a little bit different than what has been outlined in the latest issue of DSM (Diagnostic and Statistical Manual of Mental Disorders). There were 5 criteria for diagnosing people with Schizophrenia provided the individual has been experiencing the symptoms for at least 6 months. 2 out of 5 criteria are needed to make a diagnosis of schizophrenia and 1 of them must be either criteria 1 or 2:

• Hallucination
• Delusion
• Disorganised speech
• Disorganised behaviour
• Negative symptoms

There were other criteria such as the symptoms were not caused by underlying organic diseases or any substances (drug). If someone doesn't fulfil the criteria mentioned above, they will be diagnosed as schizophreniform or might be brief reactive psychosis.

The identical twin of a person who has schizophrenia has a 48% chance of developing schizophrenia. In contrast, siblings of a person with schizophrenia.

You did mention about the fraternal and identical twin later in the article, but the most important thing is the concordance rate between a monozygotic and a dizygotic twin are different (50% and 10% respectively). But since you wrote:

Studies have found that on average, identical twins are about three times more likely than fraternal twins to be concordant for schizophrenia.

I guess it is okay.

Paranoid schizophrenia is the commonest type of schizophrenia that you can find. When explaining delusion, don't forget to explain the proper definition of delusion also. Some keywords are important to differentiate between being delusional or just generally afraid of something. In my personal dictionary, delusion is an unshakeable belief which is out keeping with the social or cultural background, which is being held with conviction despite with evidence to the contrary.

Good job for making an informative article. Kudos.