My dad told it to me. I was the second backup.

Six kids here, I use the “we needed some backups” joke all the time.

As a father, this is false.

You can have humour and children at the same time...

Or people who have a sense of black humor. Never heard dads make dark puns and jokes of similar nature?

I think I’m between the comments here. I think it’s funny to say we have a spare but I also think it’s not as funny to say “oh you have a spare”. It’s like a fat guy can joke about his fatness but you can’t.