I'll write what i know about GD Peters homes in St. Petersburg.
GD Nikolaj NiKolajvitsj (the elder) Had two sons, Nikolaj and Peter. When the father died in 1891 the two sons sold the Nicolaj palace in St.Pb. The byuer was The Russian State, and in 1894 it was rented out to The Xenia Insitute. The sons shared the rest of his properties, and among other GD Peter got 3 different huge grounds in St.Pb. He also got some houses, but never lived in them, because as his son Prince Roman says: "They could not fullfill our needs". They were rented out, and GD Peter and his family had an huge income on these houses.
Before 1905 the family spent all thir time on Znamenka or Djulber, but when they had to stay overnight in St.Pb for official ceremonies ecc, they stayed by GD Nikolaj, where they had a small appartment. I belive that GD Nikolaj rented this house, situeted at Italy-street. Lateron, after his marriage, GD Nikolaj bought a ground from his brother GD Peter and built a palace on the right side of the river Neva, just in front of Oldenburg Palace, Connecetd to this ground there was another ground 13.000 m2, of GD Peters property. The Russian State wanted to buy it to build the Duma: But GD. Peter didn't sell, because he didn't agree to the idea of a Duma. On his 20. birthday, Prince Roman recieved this ground as a gift.
After 1904 the family GD Peter needed a recidence in St.Pb as the GD was promoted to General Inspector for the Ingenieur Trops. His plan was to built a recidence, but it was never realiced. They rented a Palace at the English Quai. The owner was L.D von Dervis. A few years later they changed recidence, closer to GD.Peters work, at the Fontanka-street no 22. The palace belonged to The Vonljarskij family and was like a huge villa on 2 floors. This was in 1907. As the GD Peter became a part of GD Nicolajs staff during WW1 and GDucesse Militza devoted her time to hospital work and chairity, the family never fullfilled their plans of an own Palace in SP.B, They never came back. They spent their last dramatic years on Russian ground at Djulber, Crimea.
Hope you understand my bad english
Best regards Adam.