There could be an infection starting and my need a root canal. These are the most common reasons.
Periodontal disease can run in families because the aggressive bacteria can be passed between members of the families especially parents and kids as they grow up. This is a simple answer to your question.
Many things can exacerbate them such as stress, acidic foods, trauma. and recent studies suggest vitamin deficiency ie. B 12, C, iron, folate.
There are various treatments, most are symptomatic relief. Anything over the counter with benzocaine will help with pain, Orabase,Cankaid ect.
Now, one of the best treatments is the use of a laser with will relieve pain and make the healing process much faster and is a simple procedure.