Why do my baby nieces always want me to do stuff?

I have two bay nieces, they're both 5 and look and act 7. They are very beautiful little girls but they always bug me. They always follow me, want me to play video games or watch cartoons with them, sometimes say on my lap and want me to ride them a book or they'll play on my iphone, and they get so mad when I don't pay attention to them or look away from them for too long! They put their hands on their hips and say "Will look at me or I will beat you up!" They're cute but why can't they bug their cusions. Are they trying to make me mad or something? What does this mean?

It means they like to be the center of attention

Of course they can bother their cousins or their mom or anyone else, but there's something special about you that they admire. They truly like you and like the attention you give them, so they want you to focus on them all the time.No, it's not to get you mad, all they want is your attention.