Van Morrison was not a JW.
"Van Morrison was born into the Church of Ireland, which is an autonomous province of the Anglican Communion. Members of the Church of Ireland are indeed Anglicans, and are often called "Irish Anglicans," although they are also frequently called "Protestants. Van Morrison was a Scientologist, but he later distanced himself from that denomination."
Was Van Morrison raised as a JW?
Source: Interview with Van Morrison, conducted by Stephen Davis; from the August 1985 issue of the magazine New Age; transcribed by David Chance
URL: http://www.harbour.sfu.ca/~hayward/van/reviews/1985newage.html
Davis : There's a lot of the gospel sound in your music. Is it true your family were Jehovah's Witnesses?
Van Morrison : No no no no, not really. My mother was in it for a while, a brief encounter, that was all.
Source: Interview with Van Morrison, conducted by Edna Gundersen, for Music Central online, sometime in 1997
URL: http://www.harbour.sfu.ca/~hayward/van/reviews/1997november.html
Question: Several references say you were raised a Jehovah's Witness. Is that true?
Answer: No, no, no. I wasn't raised anything. My mother went to some meetings at some point. She took me to some meetings. She didn't call herself that. It was only for a couple years' period. My father was an atheist. My mother was what you would describe as a freethinker. She would check things out and read about things, but she never joined anything.