A cristophii self seed freely for me and they flower in about 3/4 years. I also have seedlings that may be from Purple sensation or cristophii or a cross. will have to wait until they flower. Next year hopefully.

I did post a method of growing Alliums from seed on here sometime back.

Will post it again, if need be.

Sow the seed fresh. It germinates better straight from the plant rather than being dried off.
Cover lightly with grit, gravel or whatever rather than compost.
Sow in a deep pot rather than a seed tray (reasons later).
Leave exposed to weather. They need a period of cold followed by warmth to initiate germination.
When (if?) they germinate do not be in a hurry to p rick them out. This is the reason for deep pot rather than seed tray. They have only one root to begin with and if it is damaged, it dies and a new one has to be produced from the base of the seedling, usually they die.
Feed the seed pot with dilute Baby Bio type stuff, until the leaves go yellow then allow the pot to dry off.
Repotting may be done when they are dormant. Some types never really go dormant so be careful.
I often do not repot until they have had another seasons growth. Remember many of them actually grow in late winter/early spring.
Cannot think of anything else for the moment.
Not as hard as it seems.

I have plants from seed popping up in my garden that I didn't sow & its quite a distance away from the main plant, may have been a Bird or a Squirrel that dropped it LOL it's in an awkward place between the pavers & a sleeper, sleeper is starting to rot so soon I'll be able to get it out & replant it LOL
Good Luck with your seeds, nice to have a few popping up hopefully for you :o)) xx Jackie xx