My BIL (not related by blood) got a PE a few months after I got my first blood clot. He was fortunate to survive but after all the tests they found that not only did he have a genetic issue, he also passed it on to his two daughters. He takes warfarin. His daughters don't.

There is an age issue with the frequency of PE's/clots. The older you get, the more likely it is to occur and it increases at an exponential rate. When you're young, it is very unlikely to be an issue. When your old, it is more likely. Since I didn't have the genetic cause I never researched the proper age to start warfarin. Your family doctor might know. The way to ask him/her is not to say, "Should I be on blood thinners" but "At what age should I start blood thinners". The answer to the former is "No". The answer to the latter is a number you can use. He'll probably want to wait until if/when a problem manifests itself as warfarin has some side effects that are not good... especially if you aren't meticulously monitoring the dosage.