According to the footnote in the NET (New English Translation) though the Hebrew word usually denotes eunuch, it does not always mean exactly that.
In my opinion, as they were children from all over the place, they might have been placed there without being castrated. On the other hand, we know that Daniel served under the king in different officials positions, and there is no mention of his family, which might indicate to a life dedicated to service, whether because he was physically disabled or because he chose to so so.
