soudkyněmi? Wouldnt it be more natural with soudkyní? (genitive)
why is this in instrumental?
It's either "Dvě z mých tet jsou soudkyně" (Nom) or "Dvě z mých tet jsou soudkyněmi." (Ins)
Either is fine. There's a very slight difference in meaning but not something learners at your level should care or worry about.
Genitive for "soudkyně" is a no-no.
It tells me the correct answer is: Dvě z mých tet jsou sudí.
Shouldnt at the end be 'soudcí'.
Not really, soudci is masculine. Sudí is a synonym for soudce of either sex. It is not really a word we actively teach I think, your answer just happened to be close to it.
Interesting, in Czech it is possible to say "two my aunts" and also "two of my aunts". dve mé tety and dve mych tet.