Is it possible to have all three at once?
My thought was to use eldritch heritage to qualify for the Aberrant Tumor feat, but I'm not sure if it's possible to actually have all three.
By my interpretation, it should definitely possible to have the Hand and either the Eye or the Tumor.
First of all, could you link the Eyeball Familiar? Never heard of it and can't find it.
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Prerequisites: Hand’s Autonomy, Possessed Hand.
Benefit: You can remove your possessed hand, allowing the possessing spirit to animate and control its motion. Removing or reattaching your possessed hand is a fullround action. This deals no damage to you, but you can’t use the hand while it is removed. The hand acts as a wizard’s familiar, using your character level as your effective wizard level, except it doesn’t gain the alertness, share spells, deliver touch spells, spell resistance, or scry on familiar abilities. Use the statistics for a crawling hand (Pathfinder RPG Bestiary 2 59) to represent the detached hand, save that the hand isn’t undead, doesn’t have the mark quarry ability, and shares your alignment. If the hand is destroyed, the spirit regenerates your missing hand in 2d4 days. This process can be accelerated by regenerate or similar magic. You cannot use the Possessed Hand feat or any feat with the Possessed Hand feat as a prerequisite until the hand is fully regenerated. If you have the familiar class feature, you can choose for your possessed hand to become your familiar, granting it all familiar abilities as normal. If selected as a familiar, your possessed hand grants you a +3 bonus on Sleight of Hand checks.
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As long as you don't select it as your familiar, it functions as a psuedo-familiar which doesn't prevent you from acquiring a "real" familiar.
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Now while trying to provide a rule that explicitly states that you can't have more than one familiar, I realized there was no such rule. Many (myself included) interpret this clause to mean that you can only have one familiar.
Levels of different classes that are entitled to familiars stack for the purpose of determining any familiar abilities that depend on the master's level.
But on closer inspection I see that no such restriction is mentioned at all.
Here is a thread where the arguments for multiple familiars are presented.
Thread: the more the merrier! multiple familiars?
So expect table differences.
I think the eyeball is from eyebiter archetype for mesmerist.
It is indeed from the Eyebiter Mesmerist.
Now while trying to provide a rule that explicitly states that you can't have more than one familiar, I realized there was no such rule. Many (myself included) interpret this...
Does this count?
Special: If you have (or later gain) levels in a class that grants a familiar, whenever you select a familiar, you can either base your familiar's abilities on your total Hit Dice per this feat (including the restrictions on its special abilities), or choose to apply only your levels in classes that grant a familiar (and thus gain all the special abilities that familiar would grant based on those class levels). You can never have more than one familiar.
The thing about that is, it's listed in the Special section for the feat, which heavily implies that that is not a rule normally. Only if you have that feat can you only have one Familiar.
That said, I'll still have to talk to my DM about it, just in case he rules it differently. I really want to make a guy who just casually takes bits off of his body for various reasons.
The argument is muddied by some or all of those options not being "real" familiars. A FAQ says that tumors can't become improved familiars because they are just lumps of flesh. This could imply they don't count as familiars for other purposes as well.
Where is the detached hand feat from?