Well, my first genuine misunderstanding was that I didn't realise that getting married meant having the mother-in-law immediately move in with us.
She is an 86 year old lady but in quite good shape for her age, but as soon as we got married she flew out from China and into our home. She has not left since.
The woman is a widow and I know that its the right thing to do, but I simply was not expecting it.
My mother-in-law doesn't speak a word of English but she does all our cooking, and this has freed me and the wife to focus on our careers. Its not a bad thing, but it has some disadvantages.
For instance, the primary language in my own home is Mandarin, and given the language barrier, it means that I am left out of most conversations.