The same copies of the dna with the genes is distributed in all the cells of the body. This makes all the cells of the body to have the same genetic material. In lower organisms, dna replication is necessary for reproduction in order to have the same genes in the progeny.
There are two types of cells: prokaryiotic and eukaryotic.
all animal cells aka human body cells (skin, blood, etc) are eukaryotic
For the second one the answer is that they’re married