Why is my penis hard?

My first boner
When I was like a or something, I was home alone with my brothers and I
was taking a bath just minding my own business- Then all of a sudden my
dick was standing up and really hard and all that usual boner stuff. I didn' t
know what it was because my family is full of assholes who didn' t tell me
anything about puberty so I was freaking out, I literally started crying and
screaming and I yhought it was going to fall off and that I was going to have
to go to the hospital and on my god I think I can honestly say that it was
probably the most terrifying" thing I have ever experienced. So then my
brother runs in and sees me and starts laughing uncontrollably so I start
crying even harder because he used to only laugh at me when something
realty bad was happening to me and he cake my other brother in there and
they were both laughing and I was screaming at them to stop laughing while
I was crying and asking them what it was and ugh it was terrible. So then
when they calmed down they told me that it was a super power I had and alt
the boys in our family had it and that I just needed to learn to control it but I
couldn’ t talk about it with anyone but them because when you have super
powers you can' t tell anyone or you', get jealous villains. So I kept my
secret and I spent so long trying to control those powers and I got so
frustrated because I Couldnt get it to come back no matter how hard I tried,
Then a couple weeks later I got it again (when I wasn' t trying) and I was
walking around the house all proud like “oh everyone look at my powers I
got if and my mom saw it and almost screamed and then she explained the
truth to me it was really disappointing.