TB is transmitted by droplet transmission (by inhaling the droplets). When a patient who has TB, cough or spit; then the disease can be transmitted through the droplets, if u inhale the droplets.
What u need to know about TB is that it is treatable, although it requires long term therapy. If your family or friend has TB, I suggest that u should increase your immune system. Your internal immune system play a very important role in fighting TB. Take vitamins, such as multivitamins or vit B complex.
So, about the part of sex which can transmit TB, is the kissing part or the part involving saliva.
Sneezing can transmit TB too.
Hope it helps.
TB is very common in my country, especially in lower class of society.