What causes fetishes? Are they sexual disorders? Why do people have fetishes,  such as foot fetishes?
How do such fetishes form?
Are childhood incidents the main cause of fetishes?
Are fetishes a sexual disorder?
Having one or more fetishes is very widespread, and thus rather normal.


  The prevalence of fetishism is not known with certainty.[21] The
  majority of fetishists are male.[21] In a 2011 study, 30% of men
  reported fetishistic fantasies, and 24.5% had engaged in fetishistic
  acts. Of those reporting fantasies, 45% said the fetish was intensely
  sexually arousing.[23] In a 2014 study, 26.3% of women and 27.8% of
  men acknowledged any fantasies about "having sex with a fetish or
  non-sexual object".
  https://en.wikipedia.org/wiki/Sexual_fetishism


A disorder is per definiton something abnormal


  disorder [dis-or´der] a derangement or abnormality of function;
  http://medical-dictionary.thefreedictionary.com/disorder


So the answer to your question would per definition be: No. Having fetishes is normal and not a disorder.