When you were a child you already knew if you were gay. If your family was supportive you grew up and dated whom you liked. If not you his who you were and might "realize" you were gay much later in life.
A child knows who they are on the inside. This decision belongs to parents and their children. Not anyone else. It quite literally doesn't concern anybody else.
Studies have shown a very very small percentage regret their choice.
Therefore let them alone and mind your own business.