"Mum [Kath] had a major heart attack after the quake and she is in hospital," Dunn said.
"Dad [Allan] is already in hospital with cancer. The house where they live, near the stables, has taken extensive damage."
Dunn said he considered himself lucky that the stables and horses had no obvious damage.
"We worked all the horses after the quake and only one of them seems to be rattled."
Dunn won with Fastroundtown and Fiery Achiever yesterday.
Fastroundtown, having his first start, joined the stable four weeks ago.
Fastroundtown is owned by Hilderthorpe breeders Ray and Maureen Beale.
"I have been busy rearing calves and our track has been wet so I decided to send him to Robert," Ray Beale said.
He qualified the Courage Under Fire-Fast Winger gelding as a 3yr-old at Waikouaiti in January. Fastroundtown was then turned out for three months.
Fastroundtown is the fourth winner left by Fast Winger, the dam of Armbro Winger (six wins).
Fast Winger, a Wingspread mare, won three races as a 3yr-old. She traces to Robyn, who was the foundation mare for the Beales in the early 1970s. Robyn left 10 winners, including the well-performed Game Lad.
Fiery Achiever was having his second start. Fiery Achiever, also by Courage Under Fire, was bought by a group of owners including All Blacks Ma'a Nonu and Andrew Hore, after he qualified in April.