Translation of "Eldest" in Arabic

It's not easy being the eldest child.

ليس الأمر سهلا أن تكون الطّفل الأكبر في أسرتك.

Fatima is the eldest student in our class.

فاطمة أكبر طالبة في فصلنا.

Her eldest son will serve as the administrator of the estate.

إبنها الأكبر سيخدم مسؤلاً عن المؤسسة.

Planning to seize the capital, he took with him his eldest son Macrianus Minor, intending

بما أنه كان يخطّط للاستيلاء على العاصمة أخذ معه ابنه الأكبر ماكريانوس مينور

His health was failing, and in 1821, the death  of his eldest daughter left him grief-stricken.

His health was failing, and in 1821, the death of his eldest daughter left him grief-stricken.