Complete androgen insensitivity (1: 20,000 - 1:100,000 live births) causes an XY (genotype male) to be born with a female phenotype. Prior to puberty there is no obvious way to distinguish them from pre-pubertal XX females. The issues arise at puberty when they do not menstruate (no uterus or ovaries). Androgen insensitivity means telarche (sexual hair development) is delayed or absent. The vagina is usually under developed so the affected person has to dilate if they want to have penetrative vaginal sex. This is the most common form of 'intersex'.
Most affected persons have been brought up as female and identify as female, few become trans men. In many ways they are similar to trans women in that they will never menstruate or become pregnant and usually have to take some hormone supplements.
What they do not have is 'ambiguous genitalia', which is what is often meant in intersex. Either cliteromegally or micropenis. Partial (mild) androgen insensitivity causes more ambiguous genitalia with under development of male genitalia and development of breast tissue at puberty, this would be the most common cause of intersex with ambiguous genitalia.