What is good for the goose is good for the gander
«Lo que es bueno para la vaca, es bueno para el becerro
What is good for one person is good for the other, but much more especially for your couple since they share a life project in common.
First of all, let us analyze the words goose and gander. A goose is a large bird which looks like a big duck. By saying goose, we normally refer to all the species but it is important to know that in a more scientific way, goose is the term that refers to the female and gander is the one used for the male. Nowadays, and going beyond the sex battle, we might say that what is good for the wife is good for the husband. Extending the meaning, we can safely say that what is good for one member of a group is good for the others.
Wife: What are you supposed to be doing?
Husband: I am taking cough syrup. I have just developed a terrible cough
Wife: But this is not yours. It´s our son´s syrup. Go to the doctor to be prescribed.
Husband: Why spending money unnecessarily? What´s good for the goose is good for the gander.