We never know, but that bottom is a beta and become Omega for that Alpha
I don't understand the switch up either. He likes having a relationship at arms length, which is understandable but then like, he is now possessive suddenly because Noah became an omega?!? Or because of the bond?!? Alpha/omega instincts??!? He didn't care to have a family but only to possess Noah.
Yes, we only see that he is walking red flag on the street, but I hope this character development takes turned now.
If he likes keep him so close....why did he Allowed him to keep distance at the first?