10 December 1893
Dear LH,
If by "double spirit" you mean a spirit with the the appearance, memories, and personality of someone who was living and is now dead: that's just a spirit and the adjective is unnecessary. If by "doppelgänger" you mean a corporeal being with the appearance of a now-deceased person: no, those do not exist. If you in fact meant neither of those things, please clarify your inquiry.
You may also consider whether the interaction in question could have been caused by a boggart (which is the purview of this division) or by someone using polyjuice potion (which is not).
F. Greengrass
Spirit Division, Ministry of Magic
20 December 1893
Dear LH,
There are some examples of what you describe having occurred, of a person being declared dead and then their corporeal form being spotted later doing something entirely unrelated. This usually occurs because the person in question faked their death, often to avoid debts, get out of betrothals, or otherwise avoid unpleasant responsibilities.
If you believe this to have occurred with someone you know, your inquiry should more appropriately be directed to the Department of Magical Law Enforcement.
F. Greengrass
Spirit Division, Ministry of Magic