If you're able to get past the having romantic feelings for this person, it may be worthwhile keeping them in your life so long as you're both on the same page about where you're at in your platonic relationship and you're not using them solely to talk about your problems to them. Everyone needs someone they can count on in their life. If you can't get past your feelings though then that's a bit different. Hope you don't dwell on this too long!

You can always steal him.

Not everyone a person trusts/enjoys spending time with has to be their lover. Everyone needs true friends at some point in life. It's rather annoying that people can't have a good time without someone trying to turn it into a relationship instead of the great friendship it could have been.