While I get that it's something that most nobles would consider, it feels fucking insane for Sylvester to admit he had thought of disposing of Myne's family as a way to tie up loose ends, and that his reason for not doing so wasn't "oh I simply couldn't do that to my newly adopted daughter" but just that "oh, yeah she's too powerful and would throw a fit if I did it". Like, seriously?
This whole time he's been built up as a "noble, but one of the good ones" type, but that line basically paints him as just as much of a jackass as all the rest, just slightly more pragmatic in how he goes about things. It paints him as someone who doesn't genuinely care about Myne beyond what she can benefit him with, and would do bad by her if he was able to control her more (which is exactly what the other noble was trying to do here, he was just sloppier about it).
Unless this is just a bad TL/wording of "oh, I was considering disposing of them (faking their deaths just like I'm doing to Myne now)", or a "haha I just wanted to scare them there (for some likely dumb reason)" that kind of sours me on his whole character.