"Ja" is a particle you can use in a lot of situations. Pons lists some meanings with examples:
http://de.pons.com/%C3%BCbersetzung?q=ja&l=deen&in=&lf=de
So the exact translation depends on the exact context (why is it important that the boy is small?), here it's probably used to strengthen the observation, or to add an explanatory mood.
3 juli 2015
2
1
Heb je je antwoorden nog steeds niet gevonden?
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