Arabic is my native language and I am fluent in English, my wife is an English/Urdu bilingual but English is more native to her plus she can read Arabic letters without understanding it but she can’t read Urdu.
Our son is one year old now and we been using OPOL (One Person, One Language): So far my wife speaks only English and I only speak Arabic to him and we speak English among ourselves. Plus, we live in Arabic country so Arabic is the very dominating language for our son I guess.
My wife's idea is for our son to have a strong well established English and when he goes to nursery (it will be English/Arabic one) she will start speaking to him in Urdu mostly, but still English will be used when me and her speak to each other.
Basically Arabic and English are our first priority languages and we will be more than happy if our son can learn to speak Urdu.
If anyone can advise us if we going on the right path we will be grateful.