Thank you all for your encouragement and support! It helps to know I am not the only one that has had to deal with this issue. I know that the reason my family are giving me a hard time is all about their own selfish needs, which just makes me angry of course. MB, my brother is the only sibling I have who's related to my mum...don't ask very confusing family life!! My mum is very young though and still works full-time, so him being left to look after her on his own is not something that is an issue at this time or hopefully anytime soon. My brother is also married with two kids of his own. The problem is that we live in adjoining apartments and our sons are only four months apart. He wants them to grow up together as best buds. However, his wife is American and wants to go back to the States after another five years or so here, so there are no guarantees that they will grow up together anyway.
At the end of the day, I am going to do what I feel is best for both my son and I. I want to follow my own dreams in life, not someone else's and as long as I feel that my dreams would benefit my sons life then I am going to go full steam ahead!! Speaking of which, Shellbda and I have just had our offer accepted on a house in Palmerston North

Which is a great way to bring the topic up with my mum again...I shall tell her that I have invested in my future and if things don't work out in NZ I can always sell it or keep it as an investment.
Of course, I shall spend a few days pondering all of this before I sit down with mum. My brother will just have to deal, I don't actually feel the need to defend my actions to him. Much more concerned with my mum as we have always been so close and she is very close to my son as well. He loves his Nana.