B-complex is a grouping of vitamins, that share some characteristics in the metabolism of food, and forming enzymes in the body to utilize energy in the muscles and brain.

They do not help each other to get absorbed from food. Being absorbed in the GI tract is only one aspect of them.

Some help each other out in the enzymes of the body. B2 Riboflavin is part of an enzyme to activate B6 pyridoxine.
B6, folate, and B12 are involved in methylation reactions, in cells to make neurotransmitters, and to heal injuries/damage, to make new blood cells, and other tasks.
B1 is involved in the metabolism of alcohol in the body including ingested ethanol from drinking.

Much of the work in the body is either to detoxify things we consume, or to convert glucose to energy, or to rebuild damaged tissue, or to keep the blood flowing.

All the vitamins including the B-complex, do things things like this for us. They have jobs to do chemically. Our job is to provide them from a varied diet.

You can use your computer to search Google for many basic things to understand yourself. Much of this basic biology is taught in secondary schools today. If you didn't take biology in school, it might be a good idea to start reading now so you can learn to take care of yourself, and your family/pets when medical issues happen.