I know somebody who was born with a penis, raised as a boy. When only one testicle showed up, they were diagnosed as a cryptorchid, but later planned surgery to remove the retained testicle (retained testicles can become cancerous). It wasn't there. The second gonad hadn't developed properly.

She now lives very happily as the woman she always was.

Intersex people have a higher risk of being trans because intersex doesn't necessarily just affect the gonads, it can affect hormone levels, brain development, etc.