Daniel Haqiqatjou already debunked the notion that 12 yo girls don't have hips large enough to give birth. In fact, for the next 3 years, their hips only grow by 10%
Also, yes, there were hebechads. Just gotta remember Eunice's Husband. They built their own home and had no interference from any mother-in-law or such nonsense. 
The idea that all teenage islamic marriages involge the husband having to live inside the mother-in-law's house is quite suspect. Would love some source on that.