how to introduce your two year old to baby

I have a two and 3 month old I don't think he really understands what's going on he hated coming to scans as he didn't like the doctors touching his mum so he has been staying with my mum he has become very clingy and hates me leaving him so I'm unsure on how to introduce him my mum and dad are going to have him while I'm in hospital as he feels safe and he is fimilar with them and there house I don't know weather or not he should come into hospital to visit his brother or wait until we get home anyone have any experiences they can share he has also started nursery not so long ago and is enjoying it so he has become very wary of me leaving him