Rain House is probably located in the Rainwood. The only member of the house to appear or be mentioned are Tyana Wylde a wife of Lord Frey’s son Aenys who died in childbed, Ser Gawen Wylde who as master-at-arms at Storm’s End during Robert’s Rebellion had attempted to escape the castle and was caught only to die later in his cell, Ser Gladden Wylde, and Ser Willem Wylde who was a member of the Kingsguard in the last year of King Daeron II’s reign.
Information about House Wylde that reveals spoilers from the books.