He made his seven sons marry the daughters of Yasunaga ISHIKAWA and Terumasa IKEDA, and negotiated the marriage of Tadateru with the first daughter of Masamune DATE, Princess Iroha, and since Masamune became the fathe-in-law of Tadateru, Nagayasu also built a close relationship with Masamune.
また、7人の息子を石川康長や池田輝政の娘と結婚させ、忠輝と伊達政宗の長女・五郎八姫の結婚交渉を取り持ち、忠輝の岳父が政宗となったことから政宗とも親密な関係を築いていたと言われている。