So long as you are staying permanently in Dhahran, if you travel to visit your parents in Jeddah and you have decided to do ‘umrah, you have to enter ihram from the miqaat through which you pass.
But if your stay in Dhahran is temporary, then you have the choice between entering ihram from the miqaat or starting ‘umrah from Jeddah.
It says in Mataalib Ooli al-Nuha (2/298): If a person has two homes, it is permissible for him to enter ihram from the one that is closer to Makkah, but it is better for him to enter ihram from the one that is further from Makkah.
Shaykh Ibn Baaz (may Allaah have mercy on him) was asked in Majmoo’ al-Fataawa (17/54):
I am a student studying in the eastern region and my family are in Jeddah. I want to go for Hajj – from where should I enter ihram, from Qarn al-Manaazil or from my home in Jeddah?
You have the choice so long as you are one of the people who live in Jeddah closer (to Makkah) than the miqaat. But if you enter ihraam from Qarn al-Manaazil that is better since you are coming from further away, so as to be on the safe side. But if you go to your family and then enter ihram from there, there is nothing wrong with that. End quote.
Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) was asked about a married man who lives with his wife and children in Riyadh, and his mother and father are in Jeddah – what is the ruling?
He replied: If he comes to Jeddah then he is a traveller, so if he wants to go to visit his family, intending also to do ‘umrah, then we say: you must enter ihram from the miqaat, because your home is in Riyadh. As for Jeddah, it is the home of your father and mother. Hence in Ramadaan he may break his fast if he goes and visits the place where his father and mother live, if the place where he lives is in another city.
End quote from Majmoo’ Fataawa al-Shaykh Ibn ‘Uthaymeen (21/329).
And Allaah knows best.