When someone dies without leaving a dated, signed and properly witnessed will, the court decides who should receive the deceased's assets. It won't matter what your familial relationships were really like; the state will award property and cash to the survivors based solely on their legal relationship to the deceased. This is called dying "intestate". Generally only spouses, common-law spouses, and blood relatives inherit under intestate succession laws.
All this can be avoided, if you take care of things ahead of time. When you leave documents that clearly state who you wish to get your property and cash after you die, you better support your survivors in coming to terms with your death without leaving them with a lot of unnecessary distress.