Simplify the following text for a Grade 9 native English-speaking person.
Original: Throughout the 1950 's there was a rivalry with Tennis Borussia Berlin , but the idea of the two merger between the two clubs in 1958 was rejected .
Simplified: Through the 50 's an intense rivalry developed with Tennis Borussia Berlin . A proposal for a merger between the two clubs in 1958 was resoundingly rejected , with only three of the 266 members voting in favor .