^ Well, I could easily be wrong, but...
"Wild Spockian speculation"
Personally, I think the mentor/semi-uncle thing makes it icky enough, but maybe that's just me.
Wild is right. I've read a lot of Star Trek books and I've NEVER come across that!
The best source for info on Saavik's origins are contained in the novel The Pandora Principle, which I highly recommend. Saavik is indeed half-Romulan half-Vulcan, born and stranded on the aptly named planet Hellguard but...
Spock does indeed act in loco parentis
to a young Saavik in that book - it's quite touching and lovely. He makes quite the charming tutor and mentor. I will say no more except to urge you to read the book.
In the novel Vulcan's Heart, an adult Commander Saavik weds Ambassador Spock. Strictly an adult relationship. Not icky at all.
I watched The Search for Spock last night. Following on the events of TWOK as it does, and featuring so many fun moments for the original cast, I have to say I like it FAR better than almost every TNG movie, and WAAAAY more than the ST-V and ST-VI. (V makes III look like Citizen Kane.) The final moments are very moving. Don't be afraid of it -TWOK and TSFS makes an excellent double bill - TSFS is essentially the continuation of II.
I'll admit that the designs for the Vulcan costumes and sets are tres tacky however. Wouldn't you know that Abrams guys finally got a great look for Vulcan - and then they blew it up.