Yes, that counts as family history. Your doctor can decide how strong it is. Problem is that in the past people would often just die with no specific diagnosis.
DVT is life threatening. Period. Always. So if you get one you could easily die from it. Its random, depending on how it develops. The way you could die depends on where the Thrombosis develops.
So in my case it was the leg. Dont forget, one of the common side effects from estrogen is to change your cholesterol levels. High cholesterol = potential for narrowed arteries = increased probability for thrombosis. Thats why regular blood work is so important. Double ditto for very very good diet. Yes, I was advised to get my affairs in order so they were concerned.
Anyway, if in the leg, if part if the clot comes loose it will go to your lungs and cause a PE. If in your heart a heart attack (coronary). If other places, a stroke.
My personal experience. Intensely painful, leg swoll up to twice the size and could barely walk. I had heparin injections for a week or so and went on warfarin sodium which I will need to take forever. Im still here, my leg hurts every day and if Im not careful gets swollen. You need to have blood work, should be once a month but cant be bothered to check for INR (international normalized ratio) which is blood level. They then constantly adjust the daily dose up and down. You bleed very easily and when you bleed it bleeds forever. Even a tiny little paper cut. Pain in the ass.
There is a new med you can take that doesnt require the blood work but its expensive.
What else would you like to know?