Ignore what you read on Wikipedia. Much of it is wrong. I have tried to correct it but keep getting stopped. They are not that interested in the truth it seems.
People have said he doesn't have traditional Romany looks, but there is no doubt from the historical evidence. Rab was born on a piece of moorland in Dore, now a posh suburb of Sheffield. The address is given as Knoll Green Lane: which can't be found as a named road on the old maps; however there is a lane at what was Knoll Green with a well at the bottom which would have been a likely encampment. His father is listed as a besom maker. He was born on the 25 October 1867 and died on the 21st July 1937.
The name Rabbi has nothing to do with the Scots name: it is the same as the Hebrew word. Romanys often had Old Testament names.
Ernest Needham said he was "gipsy by birth."
Family history, passed down from one of Rab's nephews, has a story that he attended Rab's mother's funeral (his grandmother): he went to Howbrook to her funeral where a caravan was burnt as she was a gypsy Queen. Census and other records confirm that Selina, Rab's wife was undoubtedly a Romany.
It is not possible to trace Rab's family back with any confidence past 1861 when they appeared to go under the name of Elless and were living in Ulceby in Lincolnshire, his father being listed as an agricultural labourer. If anyone knows better I'd love to know.