This may be because of work, or to return to the country they originally came from, or because they have formed a new relationship.
The other parent may not agree with the plan. They may disagree with a reduction in the times they see their children, or may not trust the parent who wants to move to continue to promote contact. They may not be able to afford to travel for contact. They may think the plan has not been properly thought through. Older children may be telling that parent that they don’t want to go.
These cases can be very complicated, but often need to be dealt with within a short timescale.
It is therefore extremely important to get good advice as soon as possible.
Advice can look at avoiding Court proceedings.
These sorts of issues are ideally discussed and sorted out in mediation.
But if agreement cannot be reached and the case does go to Court, then success will depend on ensuring that strong evidence is presented to the Court to justify the move.