Coronavirus is a generic term for a type of virus.
For example, a few of the more common strains of the common cold, representing perhaps 15% of cases, are coronavirus - but they have no real relation to _the_ coronavirus, as term is typically used.
It depends what you mean by real relation. Both OC43 and HKU1 are betacoronaviruses, in the same genera as SARS-CoV-2. So they're genetically very similar, but there's no reliable evidence of significant cross immunity.
Coronavirus is a generic term for a type of virus.
For example, a few of the more common strains of the common cold, representing perhaps 15% of cases, are coronavirus - but they have no real relation to _the_ coronavirus, as term is typically used.