Firstly: 

There is nothing wrong with the family of the deceased receiving condolences in the graveyard, before or after the burial, whether they stand in a single row or separately, because their standing in a single row only serves to make it easy to reach them and offer condolences to them.  

With regard to their sitting in a house to receive condolences, this is not Sunnah, rather condolences should be offered to the bereaved wherever he is, in the graveyard, in the street or in the mosque. 

Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) was asked: What is the ruling on the family of the deceased forming a row at the gate of the graveyard in order to receive the people’s condolences immediately after the burial? 

He replied: The basic principle is that there is nothing wrong with that, because they are gathering in order to make it easy to reach each one of them and offer condolences. I do not know of anything wrong with that. End quote. 

And he (may Allaah have mercy on him) was asked: After the deceased has been buried and people have offered condolences to his family, they go to the house of the deceased, and that usually happens after Maghrib. Then they drink coffee and offer condolences to the family of the deceased again, and then they depart. What is the ruling on that? 

He replied: 

The ruling is that this is an innovation. At the time of the Prophet (peace and blessings of Allaah be upon him) and afterwards the Sahaabah (may Allaah be pleased with them) did not sit in their houses expecting people to come and to offer condolences. In fact this makes the calamity heavier for the bereaved because it is as if he is saying, O people, I am sitting in my house and grieving, come and offer me condolences. 

The Sunnah is for a person to close his door and then whoever sees him in the marketplace or in the mosque looking sad may comfort him with condolences, and tell him to be patient and seek reward, the matter is up to Allaah, to Allaah belongs what He has taken and what He gives, and everything has an appointed time with Him. End quote. 

And he (may Allaah have mercy on him) said: Hence the seekers of knowledge should explain this to the people and start with themselves, as we have started with ourselves. Our father died and we did not sit to receive condolences, and our mother died and we did not sit to receive condolences. If the people of knowledge did that, it would bring about a great deal of good, and the people would give up these customs. End quote from Fataawa al-Shaykh Ibn ‘Uthaymeen (17/352, 374, 389). 

And Allaah knows best.