My brothers best mate married my sister.My brother was not really happy at all.It did not change their friendship as they were mates from about 11 years of age.There divorced now and my brother and him are still best mates.However my sister and brother do no speak anymore because of this whole thing and that sucks.She thinks my brother always took his side and he probably did im not sure.To me blood is thicker than water.When i was a teen i dated my best friends brother and she didnt mind.