Last year's runner-up Mischa Zverev crashed out of the Geneva Open with a first-round defeat to Mirza Basic on Sunday.
It proved to be a bad day for the Zverev family, Alexander losing to Rafael Nadal in the Internazionali d'Italia final after being 3-1 up in the deciding set and his older brother falling at the first hurdle.
Zverev missed out on a maiden ATP World Tour singles title when he was beaten by Stan Wawrinka in a showdown 12 months ago and went out on the opening day this time around, Basic beating the eighth seed 5-7 6-3 6-4.
Basic secured the only break in the second set and needed just one in the third to move into round two in Switzerland, while Andreas Seppi saw off fellow Italian Marco Cecchinato 7-5 6-4 in the only other first-round match.
Calvin Hemery came out on top in an all-French clash in round one of the Lyon Open, seeing off wildcard Corentin Moutet 6-7 (4-7) 6-4 6-3.
Radu Albot accounted for Federico Delbonis, fighting back to pull off a 6-7 (7-9) 7-5 6-4 success.
