STBXH and I split, just found out the OW is pregnant. I've not long given birth myself and there will be months between the two babies. I have a 7 year old with autism. Am I being unreasonable that I don't want him to have to deal with a step mum and step sibling just yet within less than a year of his dad leaving and him having a new sibling already even though the new baby will be his half sibling.