half-dragons and half dragon legacies

A majority of adult dragons can shape change into a wide variety of humanoids and animals and they are capable of crossbreeding half-dragons with almost anything.   Sometimes dragons mate across species lines for true love or simple pleasure.  Other times their romances are completely utilitarian as the dragons are seeking to create half-dragons to serve as their agents.   It is common knowledge that only half-dragons conceived with humans or elves are able to conceive children of their own.     Kobolds contend at dragons can produce viable offspring with kobolds, but few outsiders believe them.   dragons commonly mated with humans in the early years of the Third Age.  A lot of nobles claim distant descent from dragons and sometimes they are not even lying.  dragons are less promiscuous in the modern age but every year sees at least one or two half-dragons conceived somewhere.   With their magical nature, draconic heritage is hard to predict. Sometimes obvious draconic traits linger in a half-dragon's descendants for a long time and sometimes their traits disappear fairly quickly.   Rather than establish set rules that say half-dragons always have X, Y, and Z, if you want to make a character that is half-dragon or has draconic ancestors it is better to customize your character with several Merits and Flaws.