Well, first of all, his mother is a pure vampire and his dad is pure human. My character is half vampire and half human. He has all the strengths of a vampire and none of their weaknesses. This means that holy water, sunlight, crosses, and stakes won't kill him. He has the speed, strength, and the ability to no die via old age. If he bites someone, it will turn them into a regular vampire. He is shunned from society because he is neither one nor the other. Although he craves blood and blood makes him stronger and faster, he fights this craving every day because he is disgusted by it.
Sure, He can change your character into a vampire, but he will only do it if your character is dieing.
How should your almost-death come about?