My mother-in-law has borderline intellectual functioning

I'm writing this after watching a documentary on borderline intellectual functioning (BIF). My in-laws are all like this, so I wanted to share that cases like this actually exist.

First off, my mother-in-law has BIF. My father-in-law has BIF too. Even my sister-in-law has BIF. But the crazy thing is, my husband is highly gifted. He graduated from a science high school, went to med school, and is now a doctor.

At first, I had no idea my MIL was borderline. I’d heard that a child’s intelligence comes from the mother (so I thought there’s no way a BIF mom could have a doctor son), they’re wealthy (I didn't think BIF people could be rich), and when I met them a few times while dating, I didn't notice anything particularly off. But after the 'Sang-gyeon-rye' (formal family meeting), things I learned through my husband, and talking to them after marriage, I realized the whole family except my husband is borderline.

Here are the weird things I noticed: - At the formal family meeting, the MIL suddenly asked my mom if she got double eyelid surgery and why her face looks so 'plump,' asking if she got fillers. - MIL can't drive. - Neither MIL nor FIL can use delivery apps. - They can't use digital devices for things like online shopping, OTT, booking train tickets, or using kiosks. - Lack of basic geography (thinks Australia is in Europe). - Very vulnerable to scams and voice phishing. - Blindly believes in superstitions and can't follow complex stories.

When I carefully brought this up to my husband, he admitted his family is borderline. He says he thinks he inherited his maternal grandfather's genes. Luckily, our kids are smart.

Edit: My in-laws are in their mid-60s. The reason they're rich is because they got lucky with land prices, and my high-IQ husband manages their assets.