Karen, The connection is through the parents of the brothers and the parents of the sisters they married. Since the profile of Mary Nolan shows no sister and no spouse, I'm guessing your question refers to the Nolan brothers and the English sisters.
Is John Nolan (Nolan-2447) one of the brothers in question? If so, he currently has no parents listed on his profile. Go to his profile edit page and add his parents by entering Nolan-2441 for his father and O'Keeffe-465 for his mother.