So, my younger brother (who still plays games) said to me today "so what game are we playing?" After a bit of confusion on my end, he said "you know what i mean, what game are we playing? On any system?" Instead of telling him that i was on a detox, i foolishly started thinking about what game we could play. Then being on a detox snapped back in my mind. 
 

So my question is, what would you do if you were in this situation and would playing a bit with my sibling, even if it's for like an hour count as relapsing?

That’s a really interesting question and something I’ve often thought about myself. My brother lives away as does a close friend I used to live with at uni, often the only interaction we have is whilst playing a game online together. Personally I probably would still count it as a relapse, especially during the 90 days. Beyond that I’d be asking myself if this is the only quality time I usually spend with my sibling, if so I’d be tempted to make an allowance if I thought it wouldn’t make cravings worse or lead to further gaming. That being said it might be nice to explore other fun ways to spend time together instead. That’s my opinion at least anyways.

I don't have any siblings so I will have to consider replacing for a friend. If my friend asks me to play a game then I would choose a multiplayer game where we control our own characters and fight like those two player games designed for one keyboard. If my friend wanted to play online through different computers then I would be very cautious about it because online games like Roblox and Minecraft are highly addictive and cause me a hard time on my detox. In conclusion, I would recommend two player fighting games on the same console/computer and never play online games because you would go back home and log in again and play for hours so you can beat your friend next time.

Try explaining the situation you are in to your sibling. Let them know that once the 90 day detox is over, you could play again, and maybe try to encourage them to follow your path? In case your sibling is supportive, that will be a great way to keep your detox up. In case they won't get it, don't get into a fight with them. Just let them know that you can not play right now because you believe that gaming is harmful to you, and ask if they would like to play anything else instead.

I second @Bugg: Some games may not be as problematic as others. Playing terraria with my gf did not cause me to relapse, but playing Overwatch with a friend totally would. I recommend you journal/think about what games will not cause a relapse, if there are any in the first place. Be very honest: if any gaming in general can cause things to get worse, then so be it. There are many more ways to spend time socializing with your sibling. 

Hope this helps,

Po