Albus Dumbledore?

I don't unserstand a few things about Dumbledore. First of all, did he love his family or not? If we did, then why did he leave them to go plan things with Gridelwald? Also, why did he plan of overthrowing the Statute of Secrecy and enslaving Muggles when he, at his present age, was always voting for Muggle rights and never said "Mudblood"?