I hope you know kannada well and hence you have asked such a question, which cannot be literally translated into English language. The word "eshtaney" cannot be exactly expressed in English language.
As far as I know, your questions asked cannot be answered as the literal translation is not possible in English languages.
I did not agree with your answer. Though this sentence is simple but in correct english with correct grammar it is difficult to form. My answer is "How many children does your father have?" But my answer is also not convincing me.I feel something is wrong in the sentence. "Naanu nanna tandege modalaneya magalu." This is simplest. I am the eldest daughter to my father. I had mentioned one more question"Nimma tandege neenu eshtaneya magalu?" Answer for this is "What is your seniority amongst the children of your father?" I want somebody to justify these statements which I have mentioned here.
in the above sentance i think problem is in amongst..but some wat it is convincing...
One sentence I know " How many children have your father? and what is your number? "
you have to ask "how many children does your father have?"
I think this should be the nearest.