The reason very basic words like Father are shared between Iranian and Spanish is because they both ultimately descend from an ancient Indo-European language likely spoken in present day Kazakhstan around 5000 years ago. Steppe pastoralists that spoke this language colonized Europe in the Bronze age. Their language evolved into the various Celtic, Latin, Slavic and Germanic languages of Europe. Greek also comes from this ancient language. Compare Latin, Greek, Avestan and Sanskrit and you will get chills at how similar they are.

Persian, English and Spanish are all Indo-European languages, albeit from their own respective sub families. English is Germanic, Spanish is Latin and Farsi is Iranic. The Scythians and Sarmatians of Eastern Europe spoke an Iranic language that probably influenced modern day Slavic languages. Arabic is an Afroasiatic language that has more in common with Hebrew or Assyrian than it does with the Iranian languages.