"Do you have children already?"
Translation:Heb jij al kinderen?
Dutch word order generally goes:
subject - finite verb - object - er/hier/daar - time - manner - place - other verbs
This is the basic structure, but it does change in certain situations. The place of the direct object of the sentence changes whether it is specific or non-specific. When the object is specific (i.e. it has a definite article - 'de' or 'het' - in front of it) it is usually placed before time/manner/place, but when the object is non-specific (no article or an indefinite article - 'een') then it is usually placed after time/manner/place.
Ik heb de pasta gisteren gegeten - I ate the pasta yesterday.
Ik heb gisteren pasta gegeten - I ate pasta yesterday.
So for this sentence, the object is after time/manner/place:
Heb jij al kinderen?
But, if the object was definite/specific, it would be:
Heb jij de kinderen al?
This site has lots of information on word order and is very useful: http://www.dutchgrammar.com/en/?n=WordOrder.00
Hope this helps!