My friends thought i was getting abused

Recently, i was playing football during break time in school when my friend group aproached me.

I said hi to them and they jusy kept quiet, after like 30 seconds of silece they asked me "Do your parents hit you" i thought it was a joke at first but they soon dissmised that thought.

The reason why they were asking is because every time they would raise their hands around or play physicly i would always cover myself, step back or just grab their arms out of instinct, and I sometimes had bruises (not scars). Thats why they came to the conclusion that i was geting abused.

After being explained why they thought i suffered abused i just burst into laughter, i explained that ever since i was young i always played rough with my brother (still do it today) he was older and stronger than me so i ofter was in the defensive, thats why i had bruises and did those things out of instinct.

Maybe i am getting punched by family but who knows.

Note: my brother doesn't normally use all his strength, so things have never gone out of control.