My friend had a date with a guy and he canceled twenty minutes before the official date time, he said his sister that he hadn't seen in a while is in town from another state and he made plans with her. Is this a good excuse? I call bullshit and say she shouldn't waste her time on him.
Keep in mind they had two dates before this where things went well
The fact that he already made plans with you means that he didn't care whether or not he keeps them. To cancel at the last minute is very wrong. he should have considered making plans with his sister for another day or at least earlier/later than your meeting that day. Unless he truly forgot about his plans with you, there's no excuse for him to have done that.
I get pissed when that happens. My boyfriend did that to me once. Once. And once only. Hell hath no fury like the hellfire Alex rained on Jason's head. He was very much aware of how giant of a mistake he made.
If your friend's guy knew the sister was coming why did he double book himself?
I would accept it but I would be cautious going forward. I would be thinkng "he didn't know she was coming in town? He just decided to call me, how long did he know he was going to need to cancel?". On the otherhand, I can see that is sister or family said that he shoukd really go out with his sister since she hasn't been here in a longtime and she will have to leave soon. So, this would make me caitious and just see how it goes from here but one more thing, and I would check out.