Norway's Filip Ingebrigtsen joked "you don't really want to be beaten by your brother" after breaking the national record in the men's mile at the Anniversary Games in London on Sunday.
Ingebrigtsen, 26, finished second behind Ethiopia's Samuel Tefera in the race, which is not an Olympic or world championship event, in a time of three minutes 49.60 seconds.
European 1500 metres and 5000m champion Jakob Ingebrigtsen, 18, set a new Norwegian national record in the 5000 metres at the London Stadium on Saturday, running 13:02.03.
"Two national records for the Ingebrigtsens is how we like it. It is what we do in training and try to push each other," said Filip Ingebrigtsen, who won 1500 metres gold at the 2016 European championships.
"You don't really want to be beaten by your brother. So with him doing a national record I thought I at least have to PB (personal best) and I think that may be the secret behind what we are doing."