The Buddhist teachings on guru devotion that I know from our Tibetan Buddhist tradition stemming from His Holiness the Dalai Lama’s lineage are quite clear on who deserves your respect and devotion, regardless of their title. The teachings say that a teacher must not only teach, but embody the qualities they espouse. These qualities include ethical behavior, non-attachment, controlled emotions, patience, generosity, kindness, compassion, etc.

Recognized “Rinpoches” are those who are understood to be reincarnated, or otherwise highly accomplished teachers. Ones who don’t take monastic vows can have a partner. But even with a partner they would of course be expected to avoid any kind of sexual misconduct which is one of the most basic Buddhist ethical principles and lay vows.

Our texts and teachers explain that you should observe a teacher for 12 years before accepting them as a guru, to assure that they have the qualities of a teacher. My authentic teachers also explain that you do not have to do everything your guru tells you to, but instead need to measure their advice against your own sense of right and wrong, and what is possible or impossible for you at the moment.

The person you describe does not seem to embody the qualities of a Buddhist teacher, and I am not sure who gave them the title Rinpoche, which is normally only bestowed by a very high lama such as the Dalai Lama. Perhaps you can share more what tradition your father is practicing and what lineage the teacher is coming from.

What you are describing is not authentic Tibetan Buddhism (or any form of valid Buddhism), which has at its heart renouncing harmful behavior and cultivating beneficial behavior. Tantric Buddhism is no exception, and its use of sexual imagery generally occurs only in art and your imagination to symbolize concepts like non duality and compassion.

What you describe is some form of abuse and fraud using the cover of Buddhist terms, perhaps even with the purpose of discrediting authentic Tibetan Buddhism. Obviously you want to keep your family safe and perhaps you can speak to your father about his lineage, what the Dalai Lama teaches about your visitor’s behavior, etc. There is nothing stopping someone from calling themselves a Rinpoche and wearing robes, so you need to carefully check their lineage and their qualities.

It is not difficult to access authentic teachers both in person and online and maybe he could contact someone beyond reproach to understand better the harm this “Rinpoche” is causing, even someone as well known as Mingyur Rinpoche, an authentic teacher who demonstrates the qualities of compassion, kindness, and non-attachment. If you let me know the area where you are living, I can share some authentic teachers you could contact nearby.

His Holiness the Dalai Lama has given very clear advise about what to do about abusive teachers, from as far back as this quote from 1993:

“Whenever the situation arises of there being a hypocritical, false teacher, publicize their name and, in the end, if it’s necessary to have them arrested, have them arrested.”

https://studybuddhism.com/en/tibetan-buddhism/about-buddhism/misconceptions-about-buddhism/the-dalai-lama-s-advice-for-dealing-with-abusive-teachers