Not directly, but it could.
B Vitamins have several benefits including increased energy from B-12, increased circulation from B-3, stress relief (from several of them), and mental stimulation from B-1. It's very possible he was just stressed and that lowered his libido; maybe the extra energy made him feel like he could; maybe the increased circulation increased it to his genitals; maybe the mental stimulation helped him see things in you that aroused him; maybe he was deficient in some of the B Vitamins that was taking away from his libido... it's hard to say for sure exactly why without running tests, but I'm glad for you that it is helping like that ;-)
I know I felt much better and generally "more alive" when I took a B Complex, so it's very likely the same "I feel better in general" effect and an extra boost down there.
Personal experience and personal research in my role as a Product Specialist for a vitamin company