I BELIEVE that the reason they moved to spiderpeople town is because during the period of time when Peter 'embraced the spider' and got organic webs, he impregnated MJ! Their unborn child was found to be severely deformed to human eyes...Still wanting their child, but afraid to raise it in a world where it would be a monster, they found Spidertown and moved there to start a new family. Peter is trying to learn to bond with the spiderkids as practice!