First time with a Cockerel: Is this concerning behavior?

[Kel2u]

I have a 15 week old Aquila cockerel and I have never had a rooster before. He, along with the nine pullets he was raised with, were integrated with my existing flock of 13 hens about a month ago. He just recently started relentlessly chasing two of the pullets he grew up with, both of which are white leghorns. Thankfully, they have lots of room to run and hiding placing he can't get to. He is just starting to crow, which he is not very good at yet, and it is hilarious!

My questions are: Is there any reason he would single out the two solid white pullets (he is black/brown and already VERY large) and leave the solid grey, solid black, and multi-colored pullets and older hens alone? Is chasing normal behavior? Also, he seems to be intimidated by the older hens, is that normal? I am debating whether to keep him or rehome him.

 

[The Coop Crew]

He probably just favors those pullets over the others. I’ve heard roosters can have favorites. He is probably chasing them to try and mate. I think it is normal for young roosters to be intimidated by the hens that are high in the pecking order as a rooster is not part of the pecking order so he knows who’s boss

 

[Hungry Chicken]

I've heard white leghorns are more timid in general (absolutely not true for our hen) so probably he sees them as easier to mate. I have definitely seen roosters chase hens to mate them. Probably he doesn't go after the other pullets he grew up with or the older hens because they're higher up in the pecking order