Three members of the same family have died in Yuen Long in what police say is a suspected murder-suicide case.

A man, 93, and his son, 69, were found with multiple stab wounds inside a flat in Chun Hing New Village after police were called at around 8pm on Tuesday.

A 19-year-old man, who was the grandson and son of the deceased, visited the flat before later falling to his death from Yuet Ping House at Long Ping Estate, officers said.

"The deceased inside the flat had a lot of injuries, and they also bled a lot, so it was difficult to conduct forensic inspections at the scene because it required a lot of cleaning work to determine the cause of death and even the number of injuries," Assistant District Commander Johnathan Kwan told the media.

"The direction of our investigation includes the background of the three deceased, their family relationships, and whether they were involved in any disputes or property disputes."