Impossible to answer, as we still don't know who he was. Some people believe that someone must have known something --he was likely covered in blood and possibly behaving strangely after the murders.
no one knows who jack the ripper is let alone how many sisters he had
5
at least 2 ..
2 were doctors
There were many stereotypes of Jewish people in Victorian London. During the murders of Jack the Ripper, many tried to pin the crimes on Jews.
I posted the information in the related links box below.
This is very difficult to answer because you did not specify who 'they' were. I'll take a guess that you mean Scotland Yard. Actually, the Jack The Ripper case is still an open case and since 1888 many people have tried to discover who the killer was. Scotland Yard stayed with the case at least until the early 1890's. I'm sure it was a great disapointment to the Yard for their failure to catch the Ripper.
Everybody seems to have their own favorite suspect as Jack the Ripper. There has never been a shortage of suspects or opinions on the identity of this notorious killer. I have studied the crimes of the Ripper and read many books on this subject including modern investigations using 21st century investigative tools and my opinion is that Walter Sickert was the Ripper. There is DNA evidence that links letters of Sickert's to some of the Ripper letters. This is but one example of the many "coincidences" that ties Sickert to the Ripper crimes.
He didn't. Jack The Ripper's crimes continued long after the murder of Mary Jane Kelly on November 9, 1888. Many believe the Ripper was still killing as late as 1891, and possibly after the turn of the 20th century.
Find a good, detailed review of Discovery Channel's "Jack the Ripper in America" at The 44 Diaries blog. It gives you a complete summary of the documentary, and includes many links and photos. Including the new composite of what detectives think Jack the Ripper really looked like.
Like many other Ripper suspects, Thompson was associated with Jack The Ripper only by the flimiest of circumstances. Thompson had trained as a medical doctor and he lived just south of Whitechapel. Other than that I could find no other reason for him to be a suspect.
he was never caught. He may have been arrested, just not for the Whitechapel murders. At the height of the Ripper killings, many people were arrested by later released. There were also people being arrested for other crimes. He could have been one of them and nobody figured out he was the killer too.