Most people would call helping a relative pay their medical bills altruism. It's also the selfish and rational choice. It's both simultaneously.

Altruism is the disinterested and selfless concern for the well-being of others. Helping your family is not altruism.

Not necessarily altruism.

It absolutely could be.

Knowing the true motives of another human is very difficult, perhaps impossible (without a predictive biological model of consciousness we can't be sure we're reading minds correctly, and it's still an open question whether such a thing can exist).