Plot problem in Hey Nostradamus (Spoilers)

So my wife and I both read hey Nostradamus and found something troubling in the second part, Jason’s story.

So Jason learns of his brother’s death
Jason sleeps with his sister in law
Sister in law gives birth to twins
Jason says the twins are his and writes letters to be given to them after his death.

But… The twins are at the memorial service. Jason’s dad Reg even makes a comment that one of them has no soul because the cells split during development. How could the twins be there at the memorial if Jason had sex with his brother’s wife right after he found out about his brother’s death? Did they wait a year to have the memorial (this wasn’t mentioned in the book).

The memorial is one year after Kent’s death. On page 53 of the hardcover US version, it says

Barb then goes on to tell Jason about Kent’s death. I don’t know why they had a memorial a year after the funeral. Maybe it’s something those wacky Youth Alive! folks do.

I am saddened that a thread on Brit-Brit having another youngun gets more responses than one concerning one Coupland’s finest books.

Have you read all of his work?

Not all, I have read:
Microserfs
Generation X
Shampoo Planet
Girlfriend in a Coma
Life Before God
Hey Nostradamus

I go back and forth between whether Hey Nostradamus or Miss Wyoming is my favorite – all the while forgetting that Life After God really is my favorite when I remember about it.