This is a Scots word, meaning 'same', used when the name of a property is the same as that of its owner: the Knockwinnocks of that ilk are the Knockwinnock family who own or live at Knockwinnock. It is often used to mean 'of the same name or family' or 'of the same type': The Davises are a family of engineers, and one of that ilk designs oil tankers; Barbara Cartland and her ilk (other writers of romantic fiction). Strictly speaking this is incorrect, and some Scots object to it quite strongly.