Several dads I know have all spoken of the difficulty of getting their young child to feel as comfortable and relaxed around them as the child's mother. Only one couple I know has the kid prefer to sleep in his dad's arms and that's because his mum is constantly stressed out when feeding him (he has some digestive issues and she has a bunch of health issues himself. Never breastfed kiddo) I dunno if it's just thousands of years of social conditioning and a bit of biology that kids gravitate towards their mum but I can fully appreciate how frustrating it can be for everyone in this modern era.