Question: Who is Mariota, Countess Of Ross's father-in-law?
Sentence (from "Mariota, Countess of Ross"): Upon the death of her brother, Alexander Leslie, Earl of Ross, she became the heir-presumptive of her niece Euphemia II, Countess of Ross although her husband Domhnall of Islay, Lord of the Isles pressed Mariota's superior claim to the earldom.
Relevant evidence: Yes