Let's just assume you're right about astrology for a minute. It is an assumption as well because lots of people think it's nonsense.
Assuming it's not, you're still basing someone's whole personality on a Sun sign. What that means is when your father was born if you drew a line from Earth to the Sun and carried it on into outer space it would hit the constellation of Libra.
The Sun isn't the only body in the solar system. There's all the other planets and the moon, and they've all got their own signs too. Then there's the way the planets relate to each other and ascendant signs.
The long and the short of it is that even if it is right there are so many other factors to take into consideration. My father and I are both Sagittarius. We are nothing like each other. I've met people who knew my dad that can't believe I'm his son.
The only way to find out what your dad is like is by meeting him. Good luck.