system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How come some siblings look way more similar to each other and some look like they are from different parents?
gpt
Everybody inherits 50% of genes from the father and 50% from the mother but these are not necessary the same 50%, they are chosen randomly. So, some siblings can have more appearance-defining genes in common, some less.