"We assume that they have children."

Translation: Wir nehmen an, dass sie Kinder haben.

[OmerKatz1]

So annehmen is to assume?

[Abendbrot]

Yes, "to assume" is "annehmen", "vermuten", "unterstellen", "voraussetzen".

[az_p]

and davon ausgehen

[Cyberchipz]

I would say more like in English "We take it that they have kids?" So take it, or take on, like we take it upon ourselves to think. or Ass u me. or literally We take (it) (up)on (ourselves) that they have children. :-) Definitely an idiom in English.

[JackDavenp5]

What is the difference between 'nehmen an' and 'annehmen'? Duolingo's translation, combined with the comments, makes me think they can be used interchangeably.

[Abendbrot]

They are the same verb. The verb gets splitted into two pieces in certain situations. The verb stays one word in sentences with an auxiliary verb.

• Ich kann annehmen, ... (=I can assume) Ich will annehmen, ... (I want to assume)

• But: Ich nehme an, .... (I assume) Ich nahm an, ... (I assumed)

• Ich habe angenommen,... (I have assumed)

[Cyberchipz]

I'm not sure, but I think I will take it upon myself to assume. :-)