Same internet, different performance?

I like to play a few games with my brother. He is sitting half a meter away from me (he is a laptop, I have a PC with a Wi-Fi adapter) and we're on the same Internet. Often it just starts to lag with me (always 2sec Internet dropouts, longer, normal lags, …) and everything runs very smoothly for him. Can anyone tell me why this could be?

WLAN is radio. Funk is unreliable. The WLAN interfaces that you use are different. So the reception quality is different. If your "WLAN adapter" is a USB stick, try repositioning it using a USB extension cable.

we're on the same internet.

Logical. There's only one internet.

Thanks and by internet I meant Wi-Fi xD

This is due to the WLAN adapter, whose antenna for reception is smaller than that of the laptop. Antennas are i.a. The best RF amplifier. The adapter also has a lower data throughput due to the fact that it is not connected directly but via plug contacts, due to contact resistances, etc.

By internet I meant Wi-Fi

I thought to myself, but one should distinguish. Different things, different problems, different solutions. You don't say "My car is broken" when the garage door is stuck.