How I Caught My Mother Having S*x With My Own Brother – Teenager Makes Shocking Revelation

For me, I would have sworn it was a mother-son affection, but it was not.
They were too close for comfort, but who would ever have suspected any fowl play. Mother paid more attention to him than she did me her only daughter.
I got jealous sometimes, but I had a very close relationship with my father to cushion the effect.
My mom was just too fond of her first son and obviously so. There were times when i tried discussing the issue of mom’s fondness with here son to my father, but he did not see it as anything but a bond of motherhood.
When I press further, he would say it is nothing but a figment of my imagination.
I have been taking JAMB classes having finished my secondary school education and was awaiting results.
Recently I had noticed that my Brother would always come home for lunch, it was not the usual, especially becuase i then had to wash some extra plates when i return from my JAMB classes.
Last week, I came home earlier than expected, it so happened that the last class of the day did not hold and it coincided with the time when my brother should be home for lunch.
I would have stayed back to hangout with friends but for the headache and the scotching weather of the day.
So I came home unannounced and what I saw would probably leave me traumatized forever.
I walked into the house quietly, the gate needed no force to open and close it, the door into the sitting run was closed but not locked.
My elder brother’s car was outside so I was sure he was there in the house, having not met anyone in the sitting room, I made for his own room but no one was there.
I was about going into my room when i heard sounds from my mother’s room. She sure was not alone, water seemed to be pouring from the shower, and no one would put it off.
So I made for my mother’s room and no one was there, there was some silence, but the shower was still running.
I thought mom had gone to the market as she said in the morning, and she had left the shower on mistakenly, just as I opened the door, I saw my mom and my brother wrapped in eachother’s arms.
I could not believe it, I did not know what to do, so I bolted off back to my tutorial centre.
Mom kept calling my phone hours later and went on to search for me. When she eventually found me, she swore it was not what i was thinking.
She pleaded that I should not tell my dad what i had seen, back in the house, my brother showed little or no remorse.
I feel so ashamed and I really want to speak out, please help advise me, should I tell my dad?