My friend was talking to me about his family last night after getting drunk.

His mother-in-law and sister-in-law came to visit and stayed at his place.
The night before last, he got off work and went home. He saw his sister-in-law wearing his wife’s sleepwear, busy in the kitchen.
Thinking it was his wife, he came up behind her and gave her a big bear hug. He didn’t expect the sister-in-law to resist—then he leaned in and kissed her hard again.
Right then, he felt a sudden hard slap on the back of his head, and his mother-in-law said from behind:
What are you so excited about—hugging and kissing like that?! This isn’t yours. Your wife hasn’t gotten off work yet!