House Baelish has a grand total of one member which is Littlefinger; unless you count Lysa after their marriage, I suppose.
Baelish's father was a sellsword from Bravos who came to the Vale and ended up a seated Knight. His lands were the smallest and poorest portion of the whole Seven Kingdoms and he took for his sigil the face of the bravosi Titan which is the giant statue you saw in today's episode.
Once Peter Baelish became the Lord of the House, he changed his sigil to the mockingbird to appear less threatening. Littlefinger is how we all know and thanks to him, House Baelish's seat is now Harrenhall which was the seat of Kings, Lord Paramount of the Riverlands and married to the Lord Paramounts of the Vale with the last living heir (as far as anyone knows) of the Lord Paramounts of the North in his care.
So, really, he's got pretty much three of the Seven Kingdoms in his pocket; even if, technically, the Riverlands were never an independent kingdom.