To be absolutely mortifed mixup of DH and BIL?

[Sexyhouseslippers]

DH brother and his wife have come over to visit DH and have a catchup before Easter. I came down to say hello etc. DH and his brother looks very similar I went up to whom i pressumed was DH and in tongue and cheek slapped his bum and muttered something like sexy. BIL turned round looking confused and blushing whilst his wife gave me a disapproving look. I'm in the toilet MN mortified and blushing.
Please tell me I'm not the only one whose done something similar.

splodgeses delightful nosh

I was once helping in a crèche for a big conference and the door was one of those stable doors where we could just shut the bottom half. At drop off time my old colleague comes up with buggy and I gush how lovely it is to see her etc and then she opens the stable door to reveal a child I don't recognise. Turns out colleague has a twin with similar aged children.