Both youngsters are plugged into a machine throughout the night which feeds food straight into their stomachs.
Aleh said their world consisted of "lots of weird pills and potions, a nebuliser of antibiotics and saline". They have daily physio to ease mucus congestion.
"On a good day we wouldn't notice but on a bad day it's like having a really bad lung infection all the time.
"It makes the whole sport thing look a bit silly. [But] it's the same thing essentially, struggling to do something."
Shefa and Yaam were born in New Zealand, spending much of their young lives in and out of Auckland's Starship Hospital before relocating to Israel in 2007 with father Shuki Shukrun and Aleh's stepmother Tali Shukrun.
The warmer climate and better access to health professionals has helped their health improve slightly.
And while Israel tried to claim Aleh as their own, the 26-year-old from Kohimarama Yacht Club says she is all Kiwi.
Of her annual trips to Israel she said: "It's so loud and everyone's in such a rush. I definitely prefer the Kiwi way of life. The family here [in Israel] is what I come for."
It was at Aleh's bat mitzvah that she told her family of her Olympic dream. Aleh cashed in her bat mitzvah cheques to buy her first racing boat.
Aleh returns to New Zealand this week where she is based fulltime. She says she is eyeing a tilt at the 2016 Olympics in Rio de Janeiro.