You’re right. The father was Johan Wilhelm Johansson (1887-1970), whose pieces are signed JWJ. He was both designer and master glassblower.
His son was the more famous Willy Johansson (1921-1993), with the signature WJ. Willy «only» designed his pieces, but didn’t execute them.
Some tend to get confused by the two similar signatures, particularly by some early 1950’s pieces that can be signed by both. The reason is that Willy designed them, while his father, the glassblower, executed them. For a few years, Hadeland art glass was signed by both designer and glassblower.
The ones signed only JWJ were both designed and executed by dad.
Hope this is clear (as glass)?
mbmb