First, if this isn't the right place, can this post be moved to the proper forum?

With all the research I've been doing, I have family members keep asking me if I've found a family crest. Really, I haven't been looking for one as i'm more concerned about documentation linking people first. But anyway, How do you know which family crest to use? What if there is no crest after a certain time period?

The way I understand this, and i'm probably wrong is, that when a husband and wife got married, they would have a new family crest made from joining their two family crests together. Then when their children got married, repeat the process.

- I was using the Charles/Diana and William/Kate as an example there. I know squat about crests.

Just looking for some help tips, so when I gt to that point, I will know what i'm looking for.

Thanks.