How can I factory reset with no passcode or itunes password?

Hi there,

My uncle recently passed and I was able to keep his iPhone 6s plus. Now my problem is that the iPhone is disabled completely due to family trying to get into the phone with no idea what the passcode could be. My other problem is that, since my uncle kept to himself, none of us know his Apple ID or the password to go with it. I've read you can do a factory reset but you need to be able to connect to itunes. Since I can't get into his itunes account for lack of password, I'm looking for help. So please can someone tell me how I can do a factory reset of the phone, I'm talking like wiping it clean back to new so that I can use the phone.

Notes:

iPhone is disabled (Message connect to itunes displayed on home screen)

No idea what the iTunes password is, so can't do a factory reset through iTunes

Need the phone wiped clean, back to brand new.

THANKS SO MUCH!!!!