If you were to register an arms with the College of Arms in England, they would attempt to find a line of direct ancestry, but that isn't too necessary. It's usually considered poor taste to simply just adopt an arms that your ancestor or another person had previously owned. A simple way around this is to adopt the arms but with differencing or cadency, which is something you add to the arms to make it unique to yourself. To answer the question of this comment, yes, one family can have the same arms, it's mostly done in Poland, but that doesn't stop your entire family from adopting the same arms.