hi i am new

hi i am new on here does anyone have advice, i recently married and my husbands son is 14 and is autistic. he has recently come to live with us, since living with us he is lying compulsively,will shout or find fault with me when his dad is not around, refuses to do anything i ask but if any family members are about he does not do these things.

i have sought advice and help but none of these things are helping, i have tried explaining consequences of such behaviour, and try to ignore a lot of it, and using rewards when he does behave i would appreciate any advice as it is getting worse. thanks