* Female horse: A female horse is called a mare.
* Young horse: A young horse, regardless of gender, is called a foal.
* Male horse: A male horse is called a stallion.
So, to answer your question directly, there isn't a specific term for a young female and a male horse together. You'd simply refer to them as a "mare and a stallion" or "foal and stallion" if they are both young.