Name changes and other gaps

As a sequel (at least in characters) to Scenes from a Marriage, I was a tad confused about some changes in the backgrounds, and what their purposes might be. For instance - in Scenes, Marianne and Johan's daughters names were Eva and Karin, while in Saraband the names have been changed to Martha and Sara.

Additionally, the age difference between Marianne and Johan is first said to be 7 years - (in Scenes, he said he was 42, while she was 35), however their ages here in Saraband are said to be 86 for Johan, and 63 for Marianne, a much more sizable gap.

And then there's the issue of Henrik. When we first met Johan and Marianne, they had been married 10 years - so taking his age of 42 and subtracting, he would've been 32 when he married her. Henrik's age was given as 61, 25 years younger than his father, which would indicate that he was born before Johan and Marianne's marriage, and no indication was ever given that Johan had had an earlier child - only Marianne was said to have had one, and it died at birth.

Yet other things remained the same - the relationship with Paula is mentioned in Saraband, so the continuity isn't completely altered. I was just curious if anyone has any insight into the alterations, and I would love to hear any explanations and/or theories!