I'm reading a series that starts with "The Beekeeper's Apprentice" by Laurie R King. Tomboyish girl of 15 walking on Sussex Downs trips over man of 50 who is watching bees, shocks him by deducing why he is watching them, as well as he could have done. He turns out to be Sherlock Holmes, she becomes his apprentice.
It is VERY platonic for the first several books, until she is in her twenties, so not exactly conventionally romantic, but certainly an odd couple, and a lot more strong bonds than a sweetie-pie romantic attachment.