But the biggest blow was dealt in March this year when their mother and "best friend" Louise Jones died, aged 52.
"Louise was an incredible mother to her children," Jack said.
"When she first got pregnant with Tegan we all knew the child was going to be smothered in love, and incredibly spoilt, Louise was born to be a mother.
"When their marriage broke down 14 years ago, both Steve and Louise continued to be the best parents they could be to their two children.
"Tegan and Ruben have always had a fantastic bond with their mother and this strengthened when their father died. She wasn't just their mother, she was their best friend too.
"She was an integral part of my life and my family's life for 30 years. Louise was a rock to us all."
Tegan is in her second year of a five-year degree studying a Bachelor of Arts, majoring in Art History, and a Bachelor of Fine Arts, at Auckland University.
Ruben is in his last year at Western Heights High School and will join his sister at Auckland University next year where he will undertake a degree in Civil Engineering.
He is currently living in Rotorua with one of his mother's best friends Tracey Curry and her husband Ross.
Curry described Louise as one of her very best friends and said she was an incredible woman who always put her children before anything else.
"She had planned to return to her hometown of Gisborne and build a house once her kids were both at university, but that obviously didn't happen. She was a wonderful, wonderful person and I miss her terribly."
Louise had taught at Westbrook Primary School for more than 20 years and was loved by staff and pupils alike.
Jack said any amount raised through Givealittle would go toward both Tegan and Ruben's ongoing daily expenses up until they could begin working.
"To have this happen to such a beautiful family is such a tragedy," Jack said. "I live in the South Island now and when I tell people about it they are often holding back tears.
"No children should have to be without both parents."
Jack said the Givealittle page was something she could do that would hopefully make a difference in Tegan and Ruben's lives.
To donate to Tegan and Ruben Allpress click here