Risk factors for carpal tunnel syndrome (CTS) are broad ranging. It's unclear if there's one single cause such as genetics, work, age, obesity, or smoking. Whether or not CTS is caused by work conditions remains a hot topic.
Some studies show repetitive movement patterns is a big risk factor. Others say 'no' -- the condition was present before work and work just made it worse. It's clear that middle-aged women (40 to 60) are at greatest risk but we don't know why exactly.
So if you and your sister are in this age bracket you fit the demographics quite well. Physical fitness (or the lack of fitness) combined with menopause, obesity, smoking, diabetes, and a small wrist size can bump up your chances of developing CTS during this time of life.
Work may be an additional factor but your own situation shows why this is still a bit fuzzy. Some people who do the same job as you and some folks who stay home can still get CTS.