Siblings are like that. My stepbro is sometimes a jackass but it's usually because his mom gave him a rough time or he had a bad day, so I don't take what he says personally.
Honestly when my sister tells me that I just shrug it off--she's older than me and shouldn't be concerned with my social life anyway, it's better to be an asshole than a mat people wipe their shoes on.
Not saying you are an asshole, because you aren't.
They just need to **censor** off.