Grandparents,parents,children – all of them under one roof. This traditional model for living is becoming less common in Germany,and so-called multi-generational homes have been decreasing in number for years now. But in these economically uncertain times,many makers of prefabricated houses say more and more of their customers are asking for multi-generational homes for extended families.Prefab manufacturer Okal is one of the companies profiting from the trend.