I think MIL/DIL problems exist everywhere, especially in places were women are still expected to remain in the home and living with the extended family. Anywhere where a MIL and DIL are expected to co-habitate there is going to be issues.

However, I don't see why the children need to be married at such a young age. If you want them to marry each other, why not wait until their over 18, why do they have to be 5?