Is it normal for a 14 year old to talk like this?

[MrsSnape]

My mums husband was out at his mother's house. My mum said "what is he doing, he's been ages!" and so my sister (14) said "probably having sex with grandma" My mum said "thats not funny, stop saying such daft things" so when he came home sister said "isn't that right? you've been having sex with grandma?"

She was not at all embarrassed and went off in a sulk saying nobody in that house could take a joke. I said this is not how a normal 14 year old speaks, is it?

She's recently been assessed for aspergers but they reckon she doesn't have it.

no

You have posted about your sister in the past, and I think you are right: there is something that does seem to raise concerns. Just hard to know what it is or how to deal with it. You would expect a 14yo to feel this is a disgusting thought.

it sounds a bit disinhibited

I am not surprised the question of Aspergers has come up

perhaps she has a really mild form

she probably didn't mean to cause offence

So she didnt show any signs of understanding that;
talking in that way is not polite
sex between mother and son is not normal

and no teenage self consciousness about it?

Did she misunderstand what sex is?

My 14 year old (DS) certainly wouldn't talk like that - he thinks anything to do with sex and older generations is pretty much disgusting, and (pretend) glares at me and DH if we kiss too enthusiastically when he's around.

So I'd agree that she is behaving in an unusual way, and appears not to have a typical reaction for a teenager. I know you've posted about her before, and thought that the suggestion of Aspergers could well be correct. But then, some people are just not good at social cues without having anything that could be labelled.