I had one boss about a decade ago that suspected I wanted her job. I was her kids' age and she knew I was ambitious and before she hired me as her Deputy, she asked if I thought I'd have her job one day. I said, very honestly, no, that I needed to diversify my experience. But I think part of her always suspected I was after her, while the other half of her leaned heavily on me and appreciated my work as her second in command.
Anyway, she's still in that same job, so there never would have been any time for me to take over for her! I think she truly enjoyed working and certainly had enough money to retire, so she wouldn't be jealous of me beating her. But I find it funny to contemplate what she'd think about having asked me if I wanted to replace her - about her suspicions that I was out for her job! - now having the evidence that I truly never was.