The easiest way to get a familiar as a sorcerer is to get the Arcane Bloodline. Since you're going for the Mutated bloodline, this might not be a possibility, not even with crossblooded.
The second possibility is having the Eldritch Bloodline feat, and picking Arcane as it. This would grant the 1st level power of that bloodline (familiar). This has the extra toll of two feats, though. One for Eldritch and the other for the prereq for the arcane bloodline, Spell focus: Knowledge (Arcane).