what does Islam say for a male who is in such situation:-
1. has a functional male organ , but small size , testes are also small like a child's.
2. intense desire to live like a female
3. have male-breasts of some sort
4. some people , on his back , call him Mukhannas (Eunuch) and make fun of him. some even before him discuss the topic of Eunuch indirectly to make fun of him and ridicule him; causing a lot of emotional & psychological pain & unrest.
Sometimes he becomes so desperate that he thinks to marry Man after Sex Reassigned Surgery or something like this. Sometimes he thinks marrying a girl much younger than him can be safer for him .
Kindly do take this case urgently. And pray for him so that he can't go astray or deviant ways.

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

If your sexual organ is so small that you cannot have sexual intercourse with your wife, then this will be a defect that gives your wife the right to revoke the contract of marriage, since she will lose the right of enjoyment.

Thus, you have to inform your wife of this issue so that she becomes fully aware of that. And if you do not tell her, then this will be a form of cheating.

The Prophet said: “Whoever cheats is not one of us (i.e. will not be considered a faithful follower of my path).” [Muslim]

Here, it is permissible to seek the advice of doctors.

On the other hand, if your organ is small but can function well and normally, then there is no problem and your wife has no right to annul the marriage. In this case, you are not permitted to make any change in your organ by medical operation, since this will constitute a state of changing the Divine Creation for the sake of enjoyment.

The Prophet cursed whoever changes the Divine Creation for the sake of sensation and enjoyment as recorded by Al-Bukhaari and Muslim from Ibn Mas’ood .

In this context, we state that if it is meant by “Medical means of beautification” to resort to operation for the sake of treating some defects that misshape, hurt or produce deformity in one's body, then this is lawful. But, if the operation is carried out for the sake of beautification or enjoyment such as enlarging one's organ or breast or making breast, lips or nose smaller, this will be unlawful because it is a form of changing the Divine Creation and following the steps of the Devil.

Allah Says (what means): {They call upon instead of Him none but female [deities], and they [actually] call upon none but a rebellious Satan. Whom Allah has cursed. For he had said, "I will surely take from among Your servants a specific portion. And I will mislead them, and I will arouse in them [sinful] desires, and I will command them so they will slit the ears of cattle, and I will command them so they will change the creation of Allah." And whoever takes Satan as an ally instead of Allah has certainly sustained a clear loss.} [Quran 4:117-119]

No doubt that one who changes the creation of Allah is cursed by the tongue of Allah's Messenger .

Ibn Mas’ood narrated that the Prophet said: “Allah has cursed female tattoo makers and those females who get tattooed, and those who have their superfluous hair plucked from their faces, and those woman who get their teeth filed for beauty, and thus interfere in Allah's Creation. A woman (Umm Ya’qoob) asked Ibn Mas’ood. 'What is all this? He answered: Why should I not curse those whom Allah's Messenger has cursed?' Although this order exists in His Book (the Quran)”. [Al-Bukhari and Muslim]

Allah, The Exalted, Created a human being in the best form and granted them different degrees of beauty. So, whoever wants to change the natural creation of Allah, and then, to change His stature of creation, then he is eligible for curse due to committing sin.

In addition, enlarging the organ requires unveiling one's private parts, which is unlawful unless there is a dire need.

This means that such action leads to the commitment of two sins: changing the Divine Creation and uncovering the private parts for no need. That, in turn, makes the sin greater and worse.

Allah knows best.