I think I did one thing wrong...?

My little cousin is 7,and my son is 12,they get together sometimes my aunt and my aunt watches my son for me sometimes,Now Billy my cousin he is hyper and he takes medicine and yes he can be a handful,now when he ws last at my house he started a fight with my son,anything else I can deal with but hitting will not be tolerated,usually I will just tell him to sit on the sofa,but this time I said he could not come back unless his mom was with him,now he goes and tells his aunt not mom what i said and the aunt is mad at me,i should have not had the convo with my little cousin but none the less no he cant come back unless he is with his mother.Am i wrong for how I feel.