Translate the sentences into Turkish :

1. How old is your oldest brother ?

2. Hikmet has a 4 year old son.

3. How old were you in 2000 ?

4. My father got married when he was 30.

5. We have a 2 year old Van cat.

6. How old was the Republic of Turkey when Atatürk died ?

1. How old is your oldest brother ?

En yaşlı ağabeyin kaç yaşında?

2. Hikmet has a 4 year old son.

Hikmet´in dört yaşındaki oğlu var.

3. How old were you in 2000 ?

2000 yılında kaç yaşındaydın?

4. My father got married when he was 30.

Babam, 30 yaşındayken evlendi.

5. We have a 2 year old Van cat.

2 yaşındaki Van kedimiz var.

6. How old was the Republic of Turkey when Atatürk died ?

Türk Cumhuriyeti, Atatürk´ün öldüğünde kaç yaşındaydı?

Çok iyi Sufler ! 

Aferin Turkish2412 !

Umm... I have a question. If yaşındaki is wrong in all the examples, then when do you really use it? I can swear I saw the construction many times in online texts.

May be those texts were something like this ? 

Hikmet´in dört yaşındaki oğlu çok güzel konuşuyor.

 Subject                               

Hikmet´s 4 year old son is speaking very well.

Hikmet´s son who is 4 year old is speaking very well.

whereas ;

Hikmet´in dört yaşında [bir] oğlu var.

 Subject                    Object 

Hikmet has 4 year old son.

somehow the -ki particle works as a place/time adverb

like in

bahçedeki çiçek

4 yaşındaki oğlan

isnt it...

I would say it functions like an adjective to describe the subject

bahçedeki çiçek = the in-the-garden flower (the flower that is in the garden)

4 yaşındaki oğlan = the 4-year-old boy (the boy that is 4 years old)

oteldeki bar = the in-the-bar hotel (the bar that is in the hotel)

köşedeki masa´ = the in-the-corner table (the table that is in the corner).

Henry is right. The -ki word is an adjective attribute. That is why I also find

                         Hikmet´in dört yaşında oğlu var

strange. We have obviously missed something here. (That is probably why I often think Turks tend to forget the -ki´s...)

I find it difficult to see dört yaşında oğlu as the object here. If that is the object where is the subject then? Could it be that it has to do with the indefiniteness of that constituent (var/yok sentences typically introduce items for the first time)?

What if there was a real object:

                          ?Hikmet dört yaşında oğlunu bize tanıttı     ?

Dear tunci I think subject here is : Hikmet´in dört yaşında oğlu. We cant seperate it. I am thinking about why sometimes we use -ki and why sometimes we dont use it. When I have an answer I will post it

Dearest Gokuyum, I considered it  as  "to have "  [sahip olmak], therefore to me "Hikmet" is the subject who is having 4 year old son.   I mean, Hikmet is the doer who is performing the action of  "having 4 year old son " 

However, If we think your way, it makes sense too. Since " there is  a son of Hikmet who is 4 year old son " , In other words, " 4 year old son of Hikmet exists" , so the whole lot except "var [exists] " could  be considered as a subject. Your thinking is right.

 Thank you for pointing out this , Üstat.

 Hikmet dört yaşındaki oğlunu bize tanıttı     ?

We have to add  -ki  to describe his son [his son´s age] . Hikmet introduced his son whois 4 year old.

Otherwise the sentence may still make sense but semantically impossible sentence. Since it may sound like " Hikmet introduced us his son while he [Hikmet] was 4 year old. "  Logically it is impossible that Hikmet can have a child when he was 4 year old. Since sometimes we Turks drop the - iken , such as ;

Hikmet dört yaşında[y]ken ] piyano çalmaya başladı.

Hikmet started to play piano when he was 4 year old.