God didn’t consider Adam his son. It was just a creation. Jesus is his son, which is something that has to be made “with” a person apparently.

If you get into the catechism, there is a very explicit attempt by both the Catholics and the Gnostics to claim Adam and Jesus are iterations of the same original concept of a perfected man. The gnostics get extra funky with it, claiming that there are a host of good and evil spiritual beings constantly at struggle with one another. And Adam and Jesus are iterations of this struggle, as these countervailing forces tangle up with one another. The Catholics just cut through it all and insist “There’s one God and he’s always winning and anything that looks like its going bad is just part of his plan because he can’t lose”.

But if you get into Revelations, you see a lot more of the Gnostic theory leak in. And if you actually start digging into Gnostic texts, you end up with something more akin to Zoroastrianism than modern Christianity.

Also I still ascribe to the belief that old testament god and new testament god are different characters.

They definitely aren’t written consistently. But how else did you think a 4000 year old chain letter was going to shake out?