Here's a timeline leading up to the day/night of the murders.
2006
Friends said that fear of crime was the main reason why Martin and Teresa left South Africa. They emigrated to Claremont, a Perth suburb, at the beginning of 2006 and resided there for almost 7 years.
2011
Rudi commenced tertiary studies at Melbourne University and was a dean’s honour list member for science.
2012
27 October – Martin purchased a home in Buderim, Queensland.
Marli was a student at Matthew Flinders Anglican College, Buderim.
2013
Henri enrolled at Melbourne University to study physics.
Rudi graduated with a bachelor of science.
2014
Rudi was studying for a master’s degree in mechanical engineering.
Henri temporarily halted his studies mid-year in order to have what he called a “gap year”.
(Julian Jansen, an investigative reporter is presently writing a book
The De Zalze Murders: The Story Behind the Brutal Axe Attack.on the murders. His research suggests he dropped out of university after showing signs of disturbed behaviour, possibly aggravated by drugs.)
Later in the year, Martin visited South Africa and decided to pursue a new business.
In late November the family started relocating from Buderim to South Africa. According to Teresa’s sister, Narita du Toit:
Marli was the first to arrive in November because she had to attend a camp at Somerset College.
Martin and Teresa arrived on 1 December.
Henri followed some days later.
Rudi flew over mid-December.
Photos of the siblings when they were younger are included in the link.
https://www.pressreader.com/south-africa/you-south-africa/20150827/283046938218654
2015
27 January – The murders occurred 6 weeks after Rudi arrived.