Re: Attending the nikah of your own mother (or father)
I said the same thing to my mother once in my feminist mode and I got an earful 
She said tum Allah se zyada samajhdaar nahin ho, a woman has to wait a while (mourn for ~4 months) after the death of her husband before getting married again just in case she is pregnant. Centuries ago, they really did have to wait that long before it could be confirmed whether they were pregnant or not. A man obviously doesn’t need to worry about this but he should show respect for his wife’s death and wait a while before getting married again.
Realistically speaking, losing a partner is a HUGE blow and marriage would be the last thing on the surviving partner’s mind.