When their master made the determination that it was time that they stopped behaving like a conquering force and begin the business of actually growing and improving their society, he had had very strict orders for his most faithful of followers. Marry and breed. He was intelligent enough to understand that the most fervent support he would receive would come from those who were raised within close proximity to power. Those they'd managed to subjugate continued to grow their families. Some of them would be loyal, some of them would be recruits to the Resistance. It was better that the children of his Death Eaters outnumber the children of those living underneath their thumbs.