We had a great time in Berlin and in Tia's appartment. We were six adults (my brother and I and our adult kids -age 22 till 27-)and the appartment was exactly as we hoped: cosy, but also with enough space to let everybody do what he wants. And beautiful bathrooms!
Communication with Tia before arrival went smouthly and also the check inn. Kreutzberg is a very nice neighbourghood and the house is located next to the river , so with beautiful weather (which we had) you can sit and relax there.