Alien baby messed up my tree.

My legacy heir’s husband got abducted by aliens. He got pregnant. While annoyed I was like “Nothing special” I thought. “I’ve been through this before”

Except. When I look at the tree it shows the Alien Pollination lady is his mom and His dad is, well his Dad. But when I click on one his parents it shows that they are sibling in laws with each other.

For a second thought this was because I used the secret baby feature so that my Heir would show as his mom in the tree. But know my heir shows as his aunt and there is no evidence the Secret baby thing is even working anymore. 
And when I went to get a video I noticed all of his step siblings are now his cousins. But his dad’s other kids are his half siblings.

It has now dawned on me that his dad has a brother, that married my legacy heir’s sister.

I just don’t understand why the step parent relationship isn’t registering. And why the dad and alien are siblings in law with each other.

I guess soon this won’t be much of an issue since I’m moving everyone to a new save and I have just having the spouses adopt the Alien kids. But it’s still annoying. 

If this is in the wrong place feel free to move it.