from typing import Tuple


def is_parent(parent_key: Tuple[str], key: Tuple[str]) -> bool:
    """Determines if keys have parent:child relationship.

    Example using dot notation:
        is_parent(a.b, a.b.c) == True
        is_parent(a.b, a.b.c.d) == True
        is_parent(a.b, a.x.y) == False

    """

    return len(key) > len(parent_key) and key[: len(parent_key)] == parent_key