он всегда был так занят своей работ

он всегда был так занят своей работой, что не заметил, как его дети выросли

Результаты (английский) 1:

He was always so busy with their work, which is not noticed as his children grew up

Результаты (английский) 2:

he was always so busy with his work, he did not notice how his children are grown

Результаты (английский) 3:

It has always been so busy its work, that he had not noticed that, as the children have grown up