Gerald Melzer fought back from a set down to beat his brother Jurgen in the quarter-finals of the Generali Open and top seed Pablo Cuevas was surprisingly knocked out of the Croatia Open by Gastao Elias.
Older sibling Jurgen is ranked over 300 places below Gerald, but threatened to deny him a semi-final spot when the wildcard entry took the opening set before going down 3-6 6-3 6-1 in Kitzbuhel on Thursday.
Jurgen got the better of Gerald in Wimbledon qualifying last year, but five breaks enabled Melzer junior to come out on top in a rain-affected first tour-level encounter between the brothers in their homeland.
Paolo Lorenzi will be the unseeded Gerald's next opponent after the Italian fourth seed saw off Jan-Lennard Struff, while Nikoloz Basilashvili and Dusan Lajovic meet in the other semi-final.
Cuevas was denied a third title of the year when he lost to Martin Kilzan in the final of the German Tennis Championships on Sunday and the Argentina suffered more misery in Umag.
The world number 20 was beaten 3-6 6-3 7-6 (9-7) by the unseeded Elias in the round of 16, while Kilzan was brought back down to earth when he lost to fellow-Slovakian Andrej Martin.
Pablo Carreno Busta made it through to the quarter-finals with a victory against Teymuraz Gabashvili, while Joao Sousa also progressed.
Dustin Brown saved two match points to beat fourth seed Thomaz Bellucci and reach the quarter-finals of the Swiss Open, while Mikhail Youzhny, Robin Haase also progressed and Gilles Simon was trailing qualifier Thiago Monteiro 6-2 4-3 when play was suspended due to rain in Gstaad.