It's all normal in my perspective. If anything, having a twin is an oddity among ourselves. I supposed you humans are asked many questions about how and why you live with those with whom you share no genetic nor intimacy-based relationship, do you not?

["Spark twins" are wonders of nature, thus there is plenty of romanticization of a bond with someone born alongside you. The constant comparisons get annoying, even if they were each other's last defender in a hostile society.]

Granted, for four million years, most of our "family" developed into military squads.