Something is tickling my memory here, was there not a birth deformity that ran through one of these family's, a club foot or some such ?
Not that I'm aware of.
There was, or is, a propensity to develop some sort of disease of the blood, pophyrhia (? not sure of spelling), triggered by, of all things, consumption of beef.
If it gets bad enough, it drives one nuts.
George III had it, as did his sons George IV, William IV, Augustus Duke of Sussex, and Edward Duke of Kent (father of Victoria) although to a lesser extent (but none of them lived as long as their father had).
Characteristics of pophyria, although not the disease itself, have been evident in most of the family since then, with the exceptions of George VI and Elizabeth II.
It was the Portuguese, Spanish, and Austrian ruling families that, throughout the centuries, had propensities towards physical defects, about half of them caused by health conditions of the time, half of them genetic. Some of them were actually monsters, in the strictly physical meaning of the term.
The only English king (or queen) known to have a significant physical defect was, of course, the much-maligned Richard III (r. 1483-1485), who had a withered arm (not a hunched back). Richard III was a very late, and the last, child born of his mother, and the usual speculation is that it was probably polio, a condition virtually unknown during the Middle Ages and Renaissance.
When I worked at the Nebraska Department of Health, as an experiment, I showed a large copy of the only portrait of Richard III known to accurately depict him as he really was, to three physicians, none of whom had any idea who he was.
The portrait does not show him below the shoulders, and hence no withered arm is visible. But it was uncanny, that all three of them described him as probably afflicted with some sort of neuro-muscular paralysis.
It was a good thing I was wearing brown pants when one of them commented the subject was probably monogamous, faithful to his wife, which was the bull's-eye within the bulls'-eye.
Startled at this accurate perception, I asked him how he figured that out. He said the lips of the subject indicated paralysis, and so probably had great difficulty kissing.