Translation:The baby sleeps between his parents.
No, the 'in' belongs to 'tussen' here. Using inslapen here is tricky. 'De baby slaapt in, tussen zijn ouders in' or even 'De baby slaapt tussen zijn ouders in, in'. would be right, but a bit confusing :) We'd change that to something like 'de baby is tussen zijn ouders in, in slaap gevallen' (On a more gruesome note: be careful using 'inslapen' and 'laten' when referring to babies or animals et cetera; 'de hond laten inslapen' means the same as it does in the english 'have the dog put to sleep', i.e. have it euthanized.)
That's because the use of the "zijn" indicates that we aren't being told that the baby is female. If it was the intention of the writer to tell us that the baby is female, the writer would have used "haar" instead of "zijn". However, the "zijn" does not tell us whether the baby is male or female, because "zijn" can mean his or its. So it is compatible with telling us that the baby is a male - although it is not sufficient to establish this. However, it can also mean that the writer is not telling us whether the baby is not male or female. And so "its" - meaning gender unspecified - should also be acceptable.
"The baby sleeps between their parents." should be accepted. They/their is able to be used as a third person singular pronoun and has been done so since middle English. Note I was corrected with, "The baby sleeps between the parents." which doesn't make much sense in terms of a translation.
This looks like an old thread. But I think I have a new question.
In an English>Dutch exercise: Duo accepted: “De baby slaapt tussen zijn ouders.” It noted that another acceptable answer would be “De baby ... tussen ... in.”
In English “between” works just fine. “In between” might be considered wordy. Is that the same in Dutch? Or is there a shade of difference between “tussen” and “tussen in”?
Ugh, must be some weird small print rule as an exception for an exception.
De baby slaapt tussen zijn ouders.
That sounds just fine to me.
Ik slaap ergens tussen. Ik slaap tussen twee lakens. Ik slaap tussen twee lakens in.
I sleep between something. I sleep between two sheets.
welp... apparently it is a thing https://onzetaal.nl/taaladvies/advies/heen-kijken-heenkijken
But it is a style type of thing. If I were correcting an academic paper I wouldn't be bothered if the "in" was omitted. If I were correcting het groot dictee der nederlandse taal, I'd probably mark it as an error if it was omitted. https://en.wikipedia.org/wiki/Grand_Dictation_of_the_Dutch_Language