I learned YEARS ago to NOT travel with people I DO NOT KNOW EXTREMELY WELL.
It also involved a cruise (QE2 from NYC to England) and I simply have chosen NOT to visit, see, socialize or connect with common friends/associates. An elementry school principal ... I am shocked his teaching staff never boiled him in oil or tarred & feathered him.
As for this grandfather ... I hope he has a disminised mental health (medical) issue.
As for the parents and possible other siblings, professional grief theapy is a MUST. My parents lost a sibling at 3 months due to 'crib death' .. . now called SIDs (sudden infant death syndrome). My mother suffered til she died in her late 70s ... after developing dementia. I had to inform all her aides ... ask all you want about her daugters ... do not ask about any sons. She would become HIGHLY upset for hours .. asking for my surviving brother (with fear something had happened to him). Of course, it did NOT help that my brother NEVER showed up on time or even showed up for some preplanned home visit ... I don't know how he shows for his court dates as a trial defense lawyer.