Richard Follis, Family solicitor said that there was no doubt that the morphine played a part in the twins' deaths.
He said if the morphine had not been given, probably both twins would be alive today.
More top news
A man has been arrested on suspicion of murder by police investigating the death of 21-year-old Reuben Morris-Laing earlier this week.
Clear overnight then sunny during Sunday.
A cold night with long clear spells, with a sunny day ahead.