Originally Posted by
Silva Stormrage
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We have Young Jerry confirm that they are sisters so I am quite confident they are sisters in some manner. Half sisters could work but I am not sure the likelihood of them being identical by chance.
Spoiler: Likelihood
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Super-duper unlikely. Think of all the siblings you know. How many pairs of them are as identical as Susan and Diane? Now realize that with different mothers, the children are less likely to be similar.
Originally Posted by
Herpestidae
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I think Jerry said they were family, not necessarily sisters.
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Alternate dimension shenanigans seem most likely at this juncture, but just to keep things interesting I'm going to guess Diane is an alternate Sarah.