what I did is tell my son that there is a mei mei inside my tummy and as him to touch my tummy. whenever night time during his night feed, we always ask him who are each of us and himself then I will point to my tummy and say who is this? kept telling him that he is a big bro, he need to take care of mei mei, share toys with her. so far before birth, he is ok but I realised on the last week before my c-sec ( cuz we told him mei mei coming out when) he become more moody and will kept cry for no reason. think he felt it. now I cannot let him see that I was carry mei mei when he woke up or when he came back from school... or else he will be moody again. other than that, he is ok when I acknowledge him 1st then bring mei mei into the picture after that.