The body is the home of the soul here on earth for the length of the incarnation. The human body is made from the elements of the earth. Each body is newly made for the soul personality who will inhabit it.
Think of a house that is worn out. The occupant vacates and the house is demolished. A contractor comes along and uses any good materials in the new house he builds. An occupant is found and moves in. There is not necessarily any connection between the old and the new occupant at all. The new house contains what has gone before, but it is still a new house. The previous occupant of the old house may well have chosen a new house in the familiar neighbourhood or they may have chosen to find a new house in a totally different neighbourhood or even a new country, depending on what the occupant wants to experience in the new house.
The soul is eternal, the body is finite, but each is made from the elements of the old. Although there is no physical connection between the body and the soul who inhabits it, we often reincarnate near each other in time and place. When we meet others who have travelled with us through a number of incarnations, there is a knowing that transcends the physical, an instant deep connection that can be felt even over the internet.
Over time, we may well have been father, mother, child, spouse or friend to each other over multiple incarnations. That is basically why soul mate and life's mate are seldom the same thing. When they are, we are incredibly blessed.