Is it SELFISH for someone to NOT want an open relationship and/or "share" their partner with other people?

Whenever the question comes up people always seem to have to explain themselves and say things like "I don't want to share my partner", I always thought were weren't supposed to share your partner.
It's selfish
not selfish
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A total of 224 votes were cast: 93 girls and 131 guys. See detailed results
Is it SELFISH for someone to NOT want an open relationship and/or "share" their partner with other people?
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