Comparing the structures of aspirin, ibuprofen, and acetaminophen, what structural do they share?

Aspirin, acetaminophen and ibuprofen do not have close similarities based on the classification and molecular structure. Aspirin is an acetyl derivative and have more than one crystal structure. Ibuprofen, the ones available as painkiller pills, is actually a racemic form, but like aspirin, it acts by inhibiting COX enzymes to limit prostaglandin activity. Acetaminophen is not even an NSAID because it has little anti-inflammatory activity.