He was the Parker Family's illegitimate child, and it was only after he became the head of the Parker Family that the old lady – his grandmother – enjoyed such glory for a number of years. Perhaps it was her own youthful experiences that helped her understand many things, which was why, even though her son and Ellie Wilton were deeply in love, she never allowed her son to betray his wife.
The elder Mr. Parker, his father, had many women outside of his marriage. Even though he later allowed his illegitimate son to take over, he never once considered abandoning his wife for any woman.
Therefore, she wouldn't allow her own son to do such a thing either.
As a result, Hannah Browman had a particularly good relationship with the old lady. With the old lady's protection, her position as Mrs. Parker would never be taken by another woman.
Marcus Parker was fortunate to have a good memory; otherwise, it would've been impossible for him to remember such distant events.