I would argue the age of these characters is peculiar. Also, the age difference between the kids. This seems less like someone envisioning a family with a lot of kids and more someone who is delusional about the prospect of ever getting older or having children that grow up.

"I want a wife who is never older than 30 and children who never hit puberty" is delusional. That's before you get into the Mormon problem of "surplus males" and how that affects the more orthodox corners of their community. When having multiple wives becomes a status symbol, and having lots of children becomes a status symbol, but the guy/girl ratio isn't 1:3, you have to start asking what happens to all the horny, defiant, increasingly disenfranchised teenage boys who have to watch their dad marry one of the girls from their high school class.

This isn't strictly a fetish so much as it is a fantasy. While there's nothing wrong with having vague, mushy, romantic views, you do need to interrogate them a bit at some point. Especially if the fantasy is going to be the foundation for your political viewpoint.

A politics defined by a 20-something wife covered in Forever Four-Year-Olds isn't rational. A politics of eternal youth is... not going to end well.