Its often so hard to know what the best thing to do is, and often both staying or going can be painful and cause problems.
My husband is from NZ and his Mum is still there, and quite elderly, whereas my parents are here in the UK and while they're still fairly young my grandma is definately not. Whether we stay in the UK or move to NZ one of us is going to be at the other side of the world to their parents/elderly family. I have a brother and sister here in the UK with no plans to go anywhere, but my husband is an only child. His mother is well enough but definately elderly, and her last remaining sibling died recently so there aren't many people left. It makes sense for us to be closer to his Mum. But on the other hand he's been here 13 years and isn't that close to her emotionally as he's never really got on with her husband (his father died when he was a teenager), whereas I'm much closer to my family and when we have children it's going to break my Mum's heart that they are at the other side of the world.
Its really hard either way, but we know that for us, and for our future family, New Zealand is definately the best option - better quality of life, good career opportunities (for me anyway), etc. So this is the right decision, and we have accept that the right decision can also be hard and can create difficult times, but that what life is about in a way.