It is enough for that person to satisfy the judge that they find it unreasonable. Proof or admission is not necessarily required. This must be desertion in a real sense for a period of two years with no means to contact the husband or wife and no support. Two years separation with consent. Again speaks for itself.
Separation requires separate living arrangements.
It can in very limited cases be proved despite living in the same property. It does require the specific written consent of the other spouse. Does not require consent, merely the fact of separation for the required period. If you have children or step children whom you have treated as your children who are still under 18 a form must be filed with the court and served with the petition that states the proposed arrangements for the children so far as residence, care, education, and seeing the other parent are concerned. These arrangements are ideally agreed with the other parent and the Judge who considers the case must be satisfied with those arrangements to let matters progress.