You only add granted spells to your repertoire1, and there the levels are fixed. For example, Demonic sorcerers have the divine spell list, but get Slow as a granted spell.
Does it mean you cannot heighten them?
(Unless of course you make them signature spells)
The "Spell Repertoire" feature for sorcerers includes the following line:
When you add spells, you might select a higher-level version of a spell you already know so that you can cast a heightened version of that spell.
See Sorcerer (Archives of Nethys)
As you already know the spells granted by your bloodline, you can simply learn a higher level version of these spells each time you gain a level, even though they are not on your spell list.
Now, there is a "might" in that rules excerpt, which could be interpreted as advice for the player and not as a rule. While I disagree with that interpretation (simply because I have not seen the game give advice to players in that manner anywhere else in rules blocks like this one), I decided to look at what the german version of the basic rules that I have at home has to say:
Wenn du Zauber hinzufügst, kannst du eine höhergradige Version eines dir bereits verfügbaren Zaubers hinzufügen, so dass du ihn nun mit erhöhtem Grad wirken kannst
(German Grundregelwerk, Page 205)
In english, this would pretty much say the following:
If you add spells, you can add a version of a higher spell level of a spell available to you, so that you can cast it with a higher level
Now, the "available to you" is sadly still up to interpretation, but at least the german version supports my interpretation that "you might select [...]" is meant to be a rule that allows you to do just that, and not just advice for a player.
As I noted in the comments for my Answer that sparked this question, I find the Rules as Written to be lacking leading to an extremely silly conclusion and recommend all GM's make a common sense ruling that granted spells are on sorcerer's spell lists. Besides avoiding complications such as technically not being able to Heighten and questions about using wands/scrolls/staves of the spell, it also brings the features in line with similar abilities such as Clerics' Deity spells.
Your deity also adds spells to your spell list.
I firmly believe this was intended (although I don't know of any developer commentary) and hope that the language of Bloodline is updated to explicitly indicate this. Some rules seem to suggest the intention, notably Spells' Tradition and School section, which includes:
Your class determines which tradition of magic your spells use. In some cases, such as when a cleric gains spells from their deity or when a sorcerer gets spells from their bloodline, you might be able to cast spells from a different spell list. In these cases, the spell uses your magic tradition, not the list the spell normally comes from. When you cast a spell, add your tradition’s trait to the spell.
Most importantly, this ties Bloodline granted spells to Deity granted spells in a tangible way. It also suggests that the spells are "part of" the Tradition for that spellcaster (although, again, it doesn't say such explicitly).
You can only learn spells that are on your spell list and only cast spells from your Repertoire. Because the phrase "are added to your spell list" and similar are missing from granted spells, they do not qualify for learning (although they can be cast because they're in your Repertoire).
Bloodline gives you
...the type of spells you cast and the spell list you choose them from, additional spells you learn, and additional trained skills.
Sorcerer Spellcasting contains details like
You must know spells to cast them, and you learn them via the spell repertoire class feature. [Heightening Spells] You must have a spell in your spell repertoire at the level you want to cast in order to heighten it to that level.
and the Spell Repertoire class feature does not mention choosing your Bloodline's granted spells outside of the level they are gained at.
At 1st level, you learn two 1st-level spells of your choice and four cantrips of your choice, as well as an additional spell and cantrip from your bloodline. You choose these from the common spells from the tradition corresponding to your bloodline, or from other spells from that tradition to which you have access. [...] When you gain access to a new level of spells, your first new spell is always the spell granted by your bloodline, but you can choose the other spells.
It specifically notes about choosing the same spell multiple times in order to Heighten it:
When you add spells, you might select a higher-level version of a spell you already know so that you can cast a heightened version of that spell.
This in no way gives permission for you to choose spells you already have in your Repertoire, only suggests why you might want to (so that you can cast a heightened version). They distinctly did not use words such as "may" or the less formal "can" and definitely not the common game terms "are allowed to"/"have Access to" as used previously in the Class Feature "You choose these from the common spells [...] other spells from that tardition to which you have access".
You can choose them as Signature Spells because it doesn't restrict you by spell list.
For each spell level you have access to, choose one spell of that level to be a signature spell. You don’t need to learn heightened versions of signature spells separately; instead, you can heighten these spells freely.
Your bloodline grants you bloodline spells, special spells unique to your lineage. Bloodline spells are a type of focus spell. [...] Unlike other characters, you don't need to do anything specific to Refocus, as the power flowing through your veins naturally replenishes your focus pool. Focus spells are automatically heightened to half your level rounded up. Focus spells don't require spell slots, nor can you cast them using spell slots. Taking feats can give you more focus spells and increase the size of your focus pool, though your focus pool can never hold more than 3 points.
So yes, if you for example receive a spell X as a bloodline spell, that spell will be automatically heightened.
