My 13 Year Old Grandson Has Had Nose Bleeds Since

My 13 year old grandson has had nose bleeds since he was very small. I have tried to narrow down what may cause them, but they can occur in the middle of the night while he is asleep. Sometimes they last from a few minutes to an hour or more. Is there any specific etiology to look for? what do we need to be asking him? what can we do to stop them once they start? His blood pressure is good even though he is overweight. He does occasionally get a little weak and light headed, even though it's not a copious amount of blood. It can be either nostril. Any help will be appreciated.