Can't Change Family Relationship

Hey, I created 2 guy roommates. Then decided I wanted to create a child in Edit a Sim instead of adopting. However, I don't want the 2 roommates to have the newly created sim as their son, I just want 1 of the roommates to. If that makes sense. As if 1 of the roommates divorced but had a child prior. (Family tree below I guess. Sorta).

I created the child, and forgot to change the relationship status with one of the roommates. Now hes stuck as the brother instead of the son. I use the command testingcheats true, then use cas.fulleditmode, but the family relationship box does't give the option to change from a brother to a son.  (I'll show a screenshot below)

I know this is probably very very minor, and does minimal to the game itself, but it would be nice if I was able to change it, as this is how I intended it to be in the first place. I'm not too willing to restart the child as I've already started some progress on him

I also tried this command relationship.add_bit {yoursimID} {targetsimID} family_parent which I saw on a Reddit post, yet to no prevail

(Posts merged by CM)