England scrum-half Ben Youngs has withdrawn from the Lions tour to New Zealand after the wife of his brother Tom learned that she is terminally ill.
Ben, 27, is a team-mate of hooker and captain Tom, 30, at Leicester Tigers and the pair will play in the remainder of the Premiership season for the club.
Scotland scrum-half Greig Laidlaw replaces Ben Youngs on the Lions tour.
"We are a very close family and, as I am sure everyone can respect, time is now precious together," said Ben.
"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."
Tom Youngs' wife Tiffany was diagnosed with cancer in 2014 and he pulled out of England's tour of New Zealand that year to care for her.
The brothers played in Leicester's 28-23 win over Worcester on Saturday, with Tom scoring the Tigers' try.
Leicester will play at Wasps in the Premiership semi-final on 20 May, with the winners going through to the final at Twickenham on 27 May.
The Lions fly to New Zealand on 29 May and their first match is on 3 June.
Ben, who had been selected in the 41-man squad for his second Lions tour, informed head coach Warren Gatland of his decision this weekend.
"We fully understand and respect Ben's decision to stay at home," said Gatland. "Family comes first and I know from having toured with Tom and Ben in 2013 how close they are. This is a difficult and important time for them and we send Ben, Tom and their family our heartfelt thoughts."
Ben has won 70 caps for England and two for the Lions in the 2-1 series win against Australia in 2013, starting the second Test alongside Tom.
Wales' Rhys Webb and Ireland's Conor Murray are the other scrum-halves in Gatland's squad.