isn't that the reason?
i mean yeah maybe. i believe thats the reason he did that.
I thought he did it so there will be no one else to take his place and so his mother can't kill him and he'll be able to keep himself safe till he gets the title.
Her mother labeled them as failures so there’s no way her mom would choose them and you can see him shed tears when he burned them so he probably did that to put them out of their misery
Maybe they were failures but evil mom was definitely trying to make the "perfect one" and in previous life fjord died at 15 and some girl who was never seen before was brought in as the new heir. So yeah he can definitely be replaced and mom was planning this
i would like to think that ML killed his siblings from that dungeon to put them out of their misery. but maybe i'm just delulu right now.