The concept of a family crest is perpetrated by scheisters who dupe people into thinking such things even exist. There is no such thing as a "family crest". One marketer in particular has made a history for themselves by creating such a fictitious product to market, supposedly based on extensive research. You would be doing yourself a very big favor by doing a bit of research to find out the facts.

There is a long European history of special awards and accommodations bestowed on an individual for exceptional bravery or service to the government, but that is an award to that specific individual, not to the family and heirs. It was very common during the historical era of knights serving royalty. It is not transferable at all.

Any marriage is not going to affect a family heirloom at all, if indeed there really is a legitimate one in your possession.