Four Iranian Kurds who died trying to cross the Channel in high winds were members of one family who paid smugglers thousands of euros after two failed attempts to reach Britain, the Guardian has been told.

Rasul Iran Nezhad and his wife, Shiva Mohammad Panahi, both 35, and two of their children, Anita, nine, and Armin, six, drowned as they tried to reach Britain by boat, according to a relative of the family and the Iranian-Kurdish human rights organization Hengaw.

The fate of the family’s third child, 15-month-old Artin, is unknown, though French officials have said it is possible an infant also died when the vessel sank. The family was from the north-western city of Sardasht.

Speaking from Sardasht, Iran Nezhad’s brother Khalil said he had last heard from the family two days ago. He said they had crossed from Iran into Turkey during the summer before proceeding through Europe to France.

A representative from Hengaw said the family had attempted to enter the UK by train twice but failed both times, and so decided to pay a smuggler to take them by sea.

A friend of the family in Calais, who asked to be called Ali, said he had met the family about a month ago and spoken with Panahi in the lead-up to their departure for the UK. “Shiva and I were talking about the issues with going to England,” he said. “I told her: ‘This is way too dangerous, you have children. Do you think they can survive in the water if, God forbid, something happens?’ And she said, ‘It’s OK, we will do it. Everyone is going there, it’s not a problem.’”

He said the family paid a smuggler about €5,000 to €6,000 to take them on the boat. “Shiva told me they didn’t have enough money to pay the smuggler and she asked her parents and parents-in-law. They sold gold and valuables for them to pay the smugglers and they prepared the money.”