This is the most random sentence Duolingo has ever produced for me.
Could be two sons therefore spelt "sons' " so it is not wrong
The sons version of the English translation is grammatically incorrect, as it's missing an apostrophe. It's not "My sons teacher", it's "My sons' teacher". But I can't report that problem.
as an English teacher I agree with you! That's the answer I put too!!
What was the indication this was meant to be 'children' and not 'sons' for 'filhos'?
Yes, "sons" should also be accepted.
'The teacher of my two children does not eat fish' Is this incorrect ??
It didn't say how many children
Doesn't is the same as does not!
Could you also say "Meu professora deles filhos não come peixe"?
Nop. Meu professor = my teacher (male). If the teacher is mine, it cant be "deles". So, it is "o professor deles não come peixe" or "o professor dos meus filhos não come peixe"
My guess: contraction of "do os meus..."