My 3.6 yo has never really taken to her 15 month old ds. There is a lot of hitting, punching, kicking and - worst of all - whenever she can she puts her hands round her neck and squeezes tight. Obviously this is unacceptable but I feel clueless at how to deal with it. We try taking something away when she does it or giving her a cross on a chart,sometimes we put her out of the room and make a lot of fuss of her sister but nothing works. I'm aware it's better to reward good behaviour than punish bad behaviour but I can't exactly ignore bad behaviour like this. I'm worried I'm bringing up a psycho. Any wise words from --more experienced-- better mums than me greatly appreciated .