Complex sentence: A fortified building had been standing on the site since at least 1427, and was purchased in 1477 by Lorenzo and his brother Giovanni di Pierfrancesco de' Medici, who reconstructed the old building, adding a courtyard, a loggia, kitchens and stables.
Split into simpler sentences: A fortified building had been standing on the site since at least 1427, and was purchased in 1477 by Lorenzo and his brother Giovanni di Pierfrancesco de' Medici. They reconstructed the old building, adding a courtyard, a loggia, kitchens and stables.