Blood is thicker than water - Cultural Definition
The New Dictionary of Cultural Literacy Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Our loyalty to our family — that is, to our blood relations — is strong no matter how we may feel about them.
blood is thicker than water - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Family ties are closer than other relationships. For example, Nancy will drop everything to help her sister; blood is thicker than water. Alluding to the fact that water evaporates without leaving a mark whereas blood leaves a stain, this proverb was first recorded about 1412.