They will once they get big enough - they need to be planted somewhere very sheltered, preferably in temperatures of 20 deg C, when all risk of frost is past.

Many thanks for this quick reply!
While they are still in their window-sill pots, should I feed them?
Thanks!

My daughter, when a very little girl, planted an apricot kernel, and to our surprise, it grew well. She never fed it at all, and it got planted out one spring and continued to grow strongly. By the time we left that house, some 9 years later, it was a very pretty bush/tree, but, unsurprisingly it never fruited.

Thanks again, Gattina! I shall continue as I am. I'm very grateful for your advice.