I haven't heard this in a long time. When I was small, it was a punishable offense to call siblings a liar. But I could call my brother "an Ananias" with no punishment.

Noun 1. Ananias - a habitual liar (after a New Testament character who was struck dead for lying)
New Testament - the collection of books of the Gospels, Acts of the Apostles, the Pauline and other Epistles, and Revelation; composed soon after Christ's death; the second half of the Christian Bible
liar, prevaricator - a person who has lied or who lies repeatedly