Wireless Connection Problem

I had a router that was working fine, but my brother who I dont talk to has changed the router to apparently a "better" one.

Now, when I turn on my computer or laptop my home Internet does not connect. Instead of showing green bars that show the signal strength, it just shows a red cross next to my home Internet network. I tried to troubleshoot, it says security settings on computer dont match those of the network.

However, the security settings havent changed at all. The SSID, password, everything is the same. Only the router has changed.

I can connect to my wireless network on my iPhone, but having the above problems when trying to connect to computer or laptop.

Also, my sister spoke to my brother and connected on her laptop somehow. She said she connected it through my brother, I dont completely understand that.

If anyone can help, please please reply. Or PM me asap.
I hope someone can.