As maternal relatives, Morofusa's descendants were at the height of their prosperity during the reign of Emperor Horikawa, who was a biological son of MINAMOTO no Akifusa's daughter, FUJIWARA no Kenshi, as can be seen from 'members of the Minamoto clan positioned side by side as the Minister of the Left and the Minister of the Right, as well as the Major Captain of the Left and the Right Divisions of Inner Palace Guards, which has never happened before' ("Chuyuki" (diary of FUJIWARA no Munetada), the article of January 22, 1094) and from 'there are 24 modern-day kugyo (court nobility), of which more than half are from the Minamoto clan, which has never happened before' ("Chuyuki" (diary of FUJIWARA no Munetada), the article of written on August 15, 1102).
源顕房の娘・藤原賢子が産んだ堀河天皇の治世では、「左右大臣、左右大将、源氏同時に相並ぶ例、未だ此の事あらず」（『中右記』寛治7年(1093年)12月27日条）、「近代公卿廿四人、源氏の人半ばを過ぎるか、未だ此の如き事あらんか」（『中右記』康和4年(1102年)6月23日条）とあるように外戚として隆盛を極めた。