I chose the translation above, but apparently there is a second one that is correct: "Benim ablam yok ama ağabeyim var." I haven't seen the word ağabeyim before. Is ağabey a synonym for abi or is there a different usage for the two words?
"ağabey" is the exact same thing :) I did remove it as something that should be showing up in the multiple choice exercises. We do not teach that (slightly dated) spelling of it anymore.
If 'benim' in 'Benim annem' is redundant, why is it needed in 'Benim ablam'?
Abim yerine ağabeyim yazılmalı
Why sister is not translated right here like "kız kardeş" or brother like "erkek kardeş"?
"ben bir abla yok ama bir abi va" should be accepted?
You must use the possesive: Benim ablam/abim then it's correct (I think).