def rm_twin_pairs(all_pairs, twin_pairs):
    """Given all possible subject pairs, remove twins leaving only unrelated pairs.

    Parameters
    ----------
    all_pairs : list of tuple of (int, int)
        All possible subject ID pairs.
    twin_pairs : list of tuple of (int, int)
        Twin ID pairs.

    Returns
    -------
    list of tuple of (int, int)
        Subject ID pairs for all non-twins.
    """

    # Remove all pairs that are twin pairs
    return list(set(all_pairs) - set(twin_pairs))