You would call your father's sister "பெரிய அந்தை" (periya anthai) in Tamil.
In Tamil, elder sister is called "அக்கா" (Akka).
akka .. for elder thangai for younger
சகோதரி, தங்கை, அக்காள் (sagothari, thangai, akkal) sister, younger-sister, elder-sister.
In Tamil, you would call your father's sister's daughter "சகோதரி" (sahothari).
Sister's husband is called Athimber (Brahmin way of Tamil) or Maamaa
In Tamil, elder sister is called "அக்கா" (Akka).
akka .. for elder thangai for younger
சகோதரி, தங்கை, அக்காள் (sagothari, thangai, akkal) sister, younger-sister, elder-sister.
periamma
Husband of your sister is called 'aliyan' in Malayalam.
sister friend
Aunty and Uncle.
Aunt
In Tamil, you would call your father's sister's daughter "சகோதரி" (sahothari).
Sister's husband is called Athimber (Brahmin way of Tamil) or Maamaa
You should call him "sagalai"
philapple Uncle