Next of kin of MH17 passengers wrote letters to Minister of Foreign Affairs Kerry, President Putin and President Poroshenko.
They families requested full cooperation with the investigation and requested to hand over any radar and satellite data.
Status per February 14 2016 on those letters:
John Kerry did not respond to the letter sent January 5, 2016. The US Embassy in the Netherlands confirmed the letter was received.
Russia responded in early February by a letter of Rosaviatsiya. The next of kin did not receive a letter of fax, email. The letter was published by Russia Today.
Ukraine did not respond.