My whole family, from 1982 to 1989.
We were living in Australia, my parents decided in late1982 to return to the UK. But they didn't bother telling me, or my two brothers, my grandmother, my 6 uncles or my 3 aunts...all of whom we had an ongoing relationship with in Australia, at the time. Myself and my two brothers were told my father had got another job working abroad, in Hong Kong.
We didn't find out the truth until we were going through immigration at Hong Kong Airport. We stayed there a week, and then came on to the UK. My parents dropped all contact with my mother's family in Australia from the moment we left, and we were told in no uncertain terms not to contact them ourselves.
That lasted until my younger brother turned 18 in early 1989. He got drunk on his birthday and called my grandmother. To say my mother was not pleased when she found out - he'd given my grandmother our address and she'd written to my mother - is the understatement of the century.
There was no real reason for it, apart from the fact that my father was always jealous of the close relationship my mother had with her family. He left my mother for OW in late 1989, and my mother ultimately returned to Australia in 1993. I don't think her family ever really forgave her for it, she was excluded from my grandmother's will - the only one of 9 siblings that was.
My father than disappeared for more than 15 years, to avoid having to pay my mother the full amount of what he owed her in the divorce financial settlement. Even the private detective my mother hired couldn't find him. He eventually resurfaced when he retired at age 65. I've had no contact with him since 1989.