Youngs will now play no part in the latest tour, however, after learning that the wife of brother Tom, who has been battling cancer for the past three years, has been told that the illness is terminal.
A statement released via Leicester Tigers' official website read: "We are a very close family and, as I am sure everyone can respect, time is now precious together.
"The most important thing for me at this difficult time is to be able to offer as much support as I can to Tom and his family in the remaining time we all have together.
"It is a great honour to be selected as a member of the British & Irish Lions squad and I would like to thank Warren Gatland, the staff and the other players for their understanding in this situation. I wish them well and, like all rugby supporters in Britain and Ireland, hope they have a successful tour."
Both Tom and Ben will continue playing for the Tigers for the remainder of the season.