Answer:
Swedenborg was certainly influential on the modern spiritualist movement, but he was one of many people expounding their teachings/philosophies on the super-natural. He might be considered one of the fathers, but is certainly not THE father.
It should be noted that the writings of Swedenborg did indeed usher in a new age, but the new age that we have today is very different than the new age which was promoted and initiated by the writings of Swedenborg. There are many aspects of which modern spiritualists have taken from Swedenborg, especially from his work on Heaven and Hell, but they have left behind may others, such as the Divinity of Jesus Christ and the eternity of the hell, and introduced others which are contrary to what Swedenborg wrote, such as reincarnation.
As to being a father of any movement or any idea, Swedenborg would be the first to say that there is one Father, the Father of eternity, the Prince of peace.