Would it be the same for "mother and daughter"? As in " they are mother and daughter"?
Yes. That's why the 'a' is in brackets...
Tha iad màthair agus nighean.
’s e màthair agus nighean a th’ annta or is màthair agus nighean iad
You cannot use tha with a noun phrase predicate, you need copula here, or an idiomatic expression (’s e X a tha an Y). ;-)
Just when I thought it all started to make sense, and neglected to add a question mark.. thanks for the correction Silmeth. ;-)
How do we know when to use Màthair or Mhàthair? Is it that Màthair means a/any mother and Mhàthair is 'my' mother (possessive).
More poisonous pronunciation!
The pronunciation is giving us "aidhias" for "agus". That happens far too often - most occurrences of "agus" in Duolingo are pronounced "aidhias"