In special cases, can you use "one such family are" vs. "one such family is"? [duplicate]

The correctness of this sentence is more apparent when one realizes that one such family is actually the [subject] complement of the sentence. The verb form of to be must therefore agree with the subject, the genes for human haemoglobin subunits; hence, are:

One such family are the genes for human haemoglobin subunits

This issue has nothing to do with the fact that family, like many collective nouns, can be treated as both singular and plural. Rather, it is simply one of subject-verb agreement (concord).

I was taught (in American schools) that you can use "are" for cases where the members of the collection are acting as individuals. In my experience, we tend to stick with "is" if it is even vaguely plausible that we are treating the collection as a unit, just because we are trained to hear the noun-verb number agreement.

I've noticed that British speakers tend to lean toward "are". So, for example, on American TV, you could hear "Microsoft is rolling out a new product"; whereas the same headline on British TV would be "Microsoft are rolling out a new product".

For your particular case, I would sidestep the issue and rearrange the sentence:

The genes for human haemoglobin subunits are one such family.

Finally, I would like to note that Americans would use hemoglobin. (So maybe, if the article is British, the "one such family are" is OK?)