Last I heard, depending on local attitudes, potentially jail. For that matter, minors can be charged for producing images of themselves. The CSAM laws in the US tend not to draw distinctions between first- and third-party production:

https://www.ojp.gov/ncjrs/virtual-library/abstracts/blurring...

https://www.innocentlivesfoundation.org/threat-of-sg-csam/

https://www.findlaw.com/criminal/criminal-charges/child-porn...

Depends on where you are. In some places in the world, into the gulag with them.

In fact, they can get gulaged if they draw a picture of a totally imaginary 16 year old, let alone a real person. It's kind of in dispute in the US, but that'd be the way to bet. 'Course, in a lot of US states, they're also in trouble for having a "partner" at all.

In practice, they'd probably have to distribute the picture somehow to draw the attention to get them arrested, and anyway they'd be a low priority compared to people producing, distributing, or even consuming, you know, real child porn... but if the right official decided to make an example of them, they'd be hosed.

I mean there have already been people reported to police or having all accounts cancelled for the kind of images most families have of their children growing up.

This entirely ignores what happens when you have states classifying telling a child “it’s ok to be gay/trans” as child abuse, or even just being gay/trans as a sex crime - which plenty of states in the US have said that they want to do.

Typically the same states and people that actively support child abuse by banning actual sex ed, and normalizing child molestation.