Yes there is history with Trump, Kennedy and his son. A Vanity Fair article suggests there was a deal
Trump used the nomination of Neil Gorsuch to demonstrate to Kennedy how his own legacy could be preserved. He ensured that Kennedy was involved in swearing in Gorsuch ....
https://www.vanityfair.com/news/2018...edy-retirement

Probably same deal with Kavanaugh. Is there law stating who is allowed to witness these oaths?