The twin souls recognize each other instinctively when they meet.
This means that it is not a conscious recognition where both of them state that they are twin souls. It is not a physical recognition, but a recognition that happens in the soul. The twin souls are drawn to each other, they merge instinctively and become ONE the way they have always been. In order to really know that your twin soul is your twin, you must meet and merge with him/her physically. You cannot know that your twin is really your twin unless you have met and merged with him/her physically, emotionally, spiritually or sexually. The merging at the physical level is very important in order for the twin souls to ground their relationship and twin soul process on earth. This day today many say they meet their twin souls online. This can be true, but if you have not met your twin in body and felt the intense union, you will not be pushed further into your own Self as a result of the union. Sometimes twins do not unite sexually, but they can still meet physically and merge spiritually. The physical meeting itself no matter how it is can lead to the union of the energies, but with a physical aspect such as for instance sex, the twin souls are pushed further into their individual selves.
There is a huge difference between having met and bonded with the twin physically and staying in some sort of correspondence online where the communication is more intellectual than it would be if the twin souls merged physically.
If the twin souls meet physically the union will happen as a result of the deepest instincts in both of them. When you recognize your twin soul, you will see yourself in the eyes of the other half. You will feel that you have finally come home and when you talk with the other half, it feels like you have known each other forever. All of it will seem very natural and the sexual union with the twin soul will feel like the most natural thing in the world.
During the spiritual, physical and/or sexual union of the twin souls, they will experience a kundalini rising.
This means that all the chakras will be activated, they will merge at all levels. The people who experience kundalini rising feel that they have been connected with their Higher Selves and a process begins where the knowledge of you being a spiritual being becomes even more intense after the twin soul union. Kundalini rising is like getting strong electricity through your entire physical body. It can be such an intense experience, so not only will you feel an out of body experience and another state of consciousness, but you can also experience physical change afterwards as a result of the twin union and the powerful kundalini rising, because you pick up on higher spiritual energies. Very often the kundalini rising can also lead to a person being less physically grounded on earth. Exactly for this reason it is even more important to get in deep contact with the physical body in order to stay grounded on earth when it comes to the twin soul signs process.