Hi there.
There will have been options on the application where he could have informed us he was estranged and would have been asked for evidence of this, we would not expect him to make contact with parents and would not ask him to do so either.
He would need to send in evidence of the estrangement, which is normally a letter from a person of good standing who is aware of the situation i.e, Doctor, Lawyer, Teacher, Police Officer, etc who can explain the situation.
Thanks