If we have a dog, but no spouse or have a spouse but no dogs. We can either come as a guide, select another color to match our needs. Because we cannot choose a family member, but we can choose the spouse and the dog.
If we have a dog, but no spouse. Or a spouse but no dogs. We can either choose to have another one. To meet our needs. We can not choose family members. But we can choose a spouse and a dog.
If we have a dog, but there is no spouse. Or have a spouse, but no dogs. We can take one as guidelines for choosing one. In order to meet our needs. Because we cannot choose family members. But we can choose the marriage and the dog.