* New lawmakers may cooperate more with ruling family
* Main Islamist and populist opposition boycotted vote
* Election is sixth in seven years; last was in December
Liberals and candidates from some of Kuwait's more marginalised tribes have won seats in a parliament which may prove more cooperative with ruling family members after opposition Islamists and populists boycotted the election.
Saturday's election was the sixth since 2006 in the major oil producer where political upheaval and bureaucracy have held up the vast majority of initiatives in a 30-billion-dinar ($105-billion) economic development plan announced in 2010.
Kuwait has the most open political system in the Gulf Arab region but parliaments have been repeatedly dissolved over procedural disputes or for challenging the government in which members of the ruling Al-Sabah family hold top posts.
The U.S. ally has seen street protests in the past two years, including over changes to the voting procedures, but its generous welfare system and relative tolerance of dissent have helped to shield it from more serious Arab Spring-style unrest.
Shi'ites - estimated at 20-30 percent of the population - won just 7 seats in the 50-member parliament compared to 17 in the last election in December, local media said.
The mainly Islamist and populist opposition boycotted the poll in protest against a new voting system announced last year, which cut the number of votes per citizen to one from four. It said this would prevent it forming a majority in parliament.
Political parties are banned so candidates campaign independently or with links to political movements.
Before the election the emir courted groups unhappy about the new voting system and encouraged several of the country's socially conservative tribes to endorse the ballot.
The snap election was triggered by a ruling from the top court in June, which said the process leading up to the last one was legally flawed. The court also upheld the new voting system in a ruling which led to splits in the opposition.
Campaign themes have included corruption, loan relief and concern over Kuwait's $4 billion aid package to Egypt after the military overthrow of Islamist President Mohamed Mursi.
Kuwait and other Gulf states such as Saudi Arabia and the United Arab Emirates were glad to see Mursi deposed because they fear Islamist influence in their own dynastically ruled nations.
Voters also complained about a lack of development in Kuwait - one of the world's richest countries per capita.
"The parliament should focus on solving the problems of development and the youth," said retired voter Mohammed Abdelrahman, 43, casting his vote south of Kuwait City.
About 52 percent of 439,715 eligible voters cast ballots, according to an initial Reuters calculation based on voting figures posted on an Information Ministry website.
This was higher than in December when about 40 percent of voters went to the polls during an opposition boycott. Turnout in previous elections had been about 60 percent.
The assembly can pass legislation and question ministers but the emir has the final say in state matters and can dissolve parliament. He picks a prime minister who selects a cabinet.