Is this a normal brother/sister relationship?

Anonymous
My boyfriend (nearly 19) and his sister (16) are extremely close to the point it annoys me. Most of the time it's just them at home as their mother stays with her boyfriend a lot so his sister cooks for him, cleans up after him, does his washing etc. They have endless nick names for each other, they watch tv together at night while she's wearing short shorts and crop tops. He picks her up or Puns her down and tickles her silly. One minute she's bossing him around the next he's treating her like a baby. I'm also pretty certain she doesn't like me. Is this normal behaviour? I'm an only child so a bit unsure
Is this a normal brother/sister relationship?
25 Opinion