Avunculate marriage is when a person marries their own aunt or uncle. It's different from regular marriage between two people who love each other because it involves family members who are related by blood.
Now, you know how you have a mom and dad, right? Well, your mom has a brother or sister who is your aunt or uncle. Avunculate marriage means that if your mom's brother or sister got married to someone, you could also get married to their spouse's kids.
It's not allowed in many places around the world because it can cause health problems for any children that come from the marriage. That's because when relatives have kids, their DNA is too similar, which can lead to genetic disorders.
So, although avunculate marriage might seem like a way to keep things in the family, it's not usually a good idea. It's also not allowed in most places because it might lead to health problems for any kids that come from that union.