and by using the my sibling is an omega and that's why I have the tablets excuse you can easily say that you smelled of pheromones bc your sibling just had his heat or someone from your family / even stranger.
That's actually a great idea! (づ￣ ³￣)づ Wish that he would do that but that's probably not gonna happen huh (￣∇￣")
I mean, in a world were omegaverse is a thing I think this excuse would be constantly used, because they have evolved with this situation so they have learned to adapt to it's requirements. and from what I've read in the other comments nothing good is going to happen (￣∇￣")
An easy excuse for the tablets would be that he had them for precaution, to give it if there is an omega in heat or say that your sibling is an omega and you have them just in case.