But a vague jealousy, one of those dormant jealousies that develop between brothers or sisters almost unnoticed until maturity, only to burst out when one of them marries or has a stroke of good fortune, kept them constantly on the alert in a fraternal, unaggressive hostility. They did love each other, yet they kept an eye on each other.
Guy de Maupassant, Pierre et Jean
jealousy, sibling-rivalry