As you reminded in your question, sexual orientation, identity as well as many other core aspects of our personality are partially shaped by learning, experiences - nurture. On the other hand, many aspects of who we are and become, do have a biological - genetic foundation, like our temperament, and it is through specific experiences that each individual expresses and deepens more or less of these predefined tendencies. Each person is unique, this is why two or more children receiving the same parenting and education could develop as very different in their temperaments (totally genetically determined), personalities, world views, life styles and more. We can see this happening everyday. People who have more than one children know how different or opposite could their children be compared to each other, regardless of how consistently they got the same parenting, love, affection and discipline. Each person is unique and even when we could be exposed to the very same stimuli, the way each unique individual responds or reacts to them is also unique, and that's part of the richness of being a human being. We could also find siblings who were raised far away from each other with very different parenting styles and family experiences, but who could present many similarities in their temperaments, personalities and even life styles, what shows once more, how nature and nurture do play key roles.