It was to be another ten years before my cousin returned to his hometown. → Not until .

Kiến thức về cấu trúc đảo ngữ
Tạm dịch: Phải mười năm nữa anh họ tôi mới về quê.
Ta có: Not until +time/time clause + trợ động từ + S + V (nguyên thể)
=> Câu được viết lại: Not until ten years later did my cousin return to his hometown.

It was to be another ten years before my cousin returned to his hometown. → Not until __________________________.

It was to be another ten years before my cousin returned to his hometown.
→ Not until __________________________.