It seems that her Parens has found a Gifted descendant of Birna, and has sought to mold her to be a good Tytalus, in an effort to use her to divide House Bjornaer.
A Tytalus happened to find a family who seemed to have a number of Gifted descendants, and observed that Bjornaer Magi, a few times took those descendants as apprentices. biding his time, he found another such Gifted child, and claimed her as his apprentice, seeking to use her against House Bjornaer, especially when she manifested her heritage as a descendant of Birna.
With such a heritage, he would have sought to both hone her ability to take animal form, and to make her Anathema to the Bjornaer Magi. So he gave her an Affinity to Muto, but also the Skinchanger virtue.
But Birna's descendants aren't so much about regular animals, as they have a focus in Legendary Creatures, and that resulted in her developing Harnessed Magic, and a desire to design spells that would allow her to take the forms of magical creatures.
Parens don't get to hand out virtues that way. A tytalus apprentice will have self confident from their parens, anything else is themselves.
Also bjorner don't generally trace bloodlines. She can be a descendant of Birna, but Bjorner would ot have taken multiple apprentices from her family, there is no indication that Birna's bloodline has an excess of Gifted even to the degree that Mercere does.
According to Apprentices, a parens can teach an Apprentice a Virtue if he has it, or he can initiate him, if he's got a script.
The story of the bloodline comes from her Parens. It could be true, it could be false, but as long as she's in the covenant, she can take his words for granted, without being challenged much on them.
Yes, if they have the virtue for the first part. For the initiation there would have to be mystery cult lore involved, and teaching virtues is not easy as penalties accumulate.
Teaching two minor Virtues (Skinchanger and Affinity to Muto) isn't that difficult, and the two of them make perfect sense for a Parens to have, together.
Affinity with muto would be a fairly common virtue, skinchanger less so, but it does make sense for a skinchanger to have affinity with muto. The Tytalus house virtue is not hermetic, so target number to teach affinity with Muto would be 15, which is high but not unreasonable (good teacher gives +3 so teaching+com of 9).
teaching skinchanger is a supernatural, not hermetic virtue, which means it can be done easilly if it is done very early- but if the arts are opened it has a minimum teaching score requirement of 20, which means a teaching+com of 14. If the teaching score is that high t will necessitate the strong parens virtue- alternately it could have been taught (by your parens or another, perhaps hired tutor) before opening the Gift and simply raise the difficulty in opening by 15, which if it raises fro 0 would be no problem at all.
My main issue is to think through a background that really does make sense and not simply handwave things that are overly convenient and improbable.
correction- skinchanger is a minor supernatural virtue with no associated ability, which means it cannot be taught.
It does include inherent aspects of a faerie charm however (in the skin itself) so your parens may have negotiated with a faerie for you to get the virtue...
The Mythic Blood of Birna, according to HoH:MC, suggest that her descendants have Slothful as a personality trait, and the Minor Magical Focus of Legendary Creatures, and the magical ability of Form of the (Temperament) Heartbeast. I'm thinking taking the Melancholic version, and having the Skinchanger virtue be a Wild Sheep.
Also, am considering a custom spell that would allow her to change shape from a female Wild sheep to a male form. Would that be Base 2 (Make superficial change to a Beast), or Base 4 (Making Major Change to a Beast)? I am leaning towards Base 4, since it also gives you horns to use for attack.
which would imply that the skinchanger is also from her lineage
I would be fine with you skinchanging into a ram instead of a sheep despite the gender difference (assume the skin is from a ram) unless you have some reason to want to be able to switch between the two- As a muto animal I'm going to split the difference and figure that horns not being entire limbs is balanced by other effects of gender transformation (fertility and milk) and call it a base 3.
Supposedly Birna came from a tradition that had the Shapeshifter virtue.
In any case, for her Virtues, we have Mythic Blood (Birna), Minor Magical Focus (Legendary Creatures) - Free from Mythic Blood, Self Confident - Free from House, Skinchanger (Wild Goat/sheep), and Affinity with Muto, for her other Virtues, am considering Harnessed Magic, Affinity to Animal, Improved Characteristics, and Puissant Concentration. Which leaves me with one more Virtue to choose, and am debating between Student of the Magic Realm (to showcase her knowledge of Legendary Creatures), Long Winded (suitable for someone who spends her time as a Wild Goat), or Perfect Footing (same reason).
For Flaws, she gets Slothful for free from Mythic Blood, and am considering taking her Second Personality Flaw to be Lecherous (Major), Careless Sorcerer (an Hermetic flaw that showcases her slothfulness, as she tries to cut corners when casting spells), Small Frame (Wild Goats are smaller than humans), Incomprehensible (either the Tytalus training has damaged her ability to convey her ideas, or it's just hard to follow her thinking), Short-Ranged Magic (She is so focused on finding a way to change shape to a Legendary Creature, that anything further than her touch is harder for her to grasp, pun intended), and lastly Visions (She believes they come from Birna as a Great Beast, and she seeks to follow them, hoping they will lead her to Birna, which she truly believes wants her to bind her as her Familiar.)
Any of these should be fine. The only caution I would give is there is a second Tytalus character who is male and considering taking lecherous as well- this has all kinds of story opportunities, but you should at least be aware of where that might lead if you are considering taking the flaw (which you might consider a good thing).
I can see her having several lofty goals (some of them at odds with one another:
Find Birna as a Great Beast and bind her as a Familiar.
Bind a powerful Legendary Creature as a Familiar. (A Dragon, a Chimera, maybe Lou Carcolh from F&F p. 63, or something like that)
Find a way to bind more than one Familiar.
Start a menagerie of Legendary Creatures. Or maybe just a place where such creatures feel comfortable visiting and interacting with Magi in a peaceful manner.