Poor WiFi connections for android phone

[Android Central Question]

Recently i noticed my phone has poor wifi connections at HOME ONLY. A few weeks ago it was fine, but now the signal fluctuates a lot. There is an exclamation mark beside the wifi symbol sometime. My brother noticed that as soon as my phone connects to the home wifi, his wifi based devices also experience fluctuations in wifi. He states that the wifi is fine until my phone connects to it. Ethernet devices work fine.