Nine people died in the incident in Casteldaccia – from children aged one, three and 15 to their grandparents. Only three people who were outside the house at the time survived.
Three other people died when their cars were swept away elsewhere in Sicily.
Days of heavy rain and winds have killed at least 17 other people in Italy, mainly in the north and west.
Some of the worst damage was to roads around Belluno in the northern Veneto region, after days of storms had dislodged mud, rocks and water.
Six regions remain under alert – from Veneto to Sicily and Sardinia in the south.
The tragedy in Casteldaccia occurred overnight on Saturday.