We both have great-uncles named Gene who were twins. Zeke would only have to learn how to pronounce one sound. We could say this: Gene, why can't you be more like your sister Jean? Conversely: Jean, why can't you be more like your brother Gene? Zeke could say this: Hi, I'm Zeke. This is my brother, Gene. This is my sister, Jean. Shopping for jeans with Gene and Jean. Shock value.
Announcements over the intercom at school, athletic events, etc. Inevitably, they will be some who refer to our children as the Jeans (Genes?). There may be other Jeans or Genes in the same class at school, which could make an already potentially confusing situation untenable. Jean could be made fun of for having Gene's genes. Gene could be made fun of for wearing Jean's jeans. Life is long; shock value is short.