Third son

[devayaani]

Could you please tell me how I should phrase my question to get the answer from that person: " I am the third son to my father."
[Here the respondent tells me the order of his birth in his family . Let us assume he has three brothers, two elders and one younger and has no sister.]
Thanks in advance.

[legend.isgod]

Third born of 4?

[devayaani]

No. The information I have given in the bracket is just a hypothetical situation. I have to ask (and phrase it correctly) the question even if I do not know how many brothers he has.
I am not sure if I can ask: "What is your birth order in your family?"
Would he reply : "I am the third son to my parents"?

Thanks

[TCL-MUMPING]

If you merely want that person to say that phrase, why can you not ask him to repeat it word for word?

[Marijn]

I can't think of a succinct way of putting it. . . but I would ask. . . Do you have any siblings, if so; how many older than you, and how many younger?

[Quizmonster]

"In your family, which order son are you?" That offers him every possible answer from ""I'm the only son" to "Second", "Third" or whatever.

[TCL-MUMPING]

I'm confused as to whether you are wanting to receive the specific response "I am the third son to my father" or just the position in relation to any number of brothers. Also how many folk would use the construction "to my father" in that context?

[vascop]

How many brothers do you have who are older than you?
If the answer is 10 then he must be the 11th etc.

[devayaani]

Thank you everyone for your suggestions.
TCL-MUMPING, I am sorry I know I have confused you. Yes, you are correct my intention was to get the person's position in relation to his brothers (all other siblings) not a specific answer such as the one I have used "I am the third son to my father."
It came to my mind (I was unable to phrase the right question) when I watched an old Hollywood film where the man says "I am the third son to my father." In the film the character had made that statement in a confrontation but no question was put to him. That made me wonder (and frustrated me) how to ask the question to get such an answer (in the unlikely circumstance, as you quite rightly said).
Thanking you once again.