1 definition by Toyotarox

For children growing up in spilt families, When a parent remarries and has further children they are half brothers and sister.
When the parent who has left then has children the two young half siblings are unrelated. these are semi siblings.

Your parents first spouse's children. usually the half siblings of your half siblings.
My sister's Father's daughter is my semi sister.

My Brother's mother's son is me semi brother

They are both my semi siblings
by Toyotarox October 3, 2009
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