Is this a normal whirl or am I thinning

[adzelg]

Hello I’m an 18 year old , I have never really look at the back of my head and I can just noticed my crown/whirl and I have naturally thin curly hair so it didn’t bother me for the most part but I told myself what if so please let me know if it’s thinning, literally everyone in my family has hair even my mums dad he had a full head of hair with nw2 hairline before he passed at 50, my dad started losing his hair because of severe stress he had an amazing hairline and hair at my age as I’ve seen in pictures but yeah he started losing his hair because of severe stress as my Mum and dad were both struggling growing up together so he just decided to shave it off so please let me know what you guys think here’s a picture with flash and without flash