Do your siblings have a habit of going through your stuff? If yes, then you could buy a small safe as those things ain't too expensive ( you can find basic models for ~$50). If no, then there must be a place in your room where you can safely store it.
The thing is that everyone pocket is not the same while $50 might look not expensive, to another it could be an expensive sum. So in the case where the $50 for a safe seems to be expensive then you can boldly write your seed phrase down in a plain sheet and have it placed where you keep your important documents like your certificates and major project works, as your siblings won't wanna tamper with your certificates knowing the usefulness of them, this thereby also keeps your seed phrase safe from them too. Mind you, my advise is only a cost effective one, in case you can't afford a safe.
