Your flesh and blood is your own family, whom you cannot disown. He is your flesh and blood.
It is used to insist on an obligation rather than to describe a relationship. To be told somebody is your flesh and blood is an argument rather than a fact.
1phraseyour flesh and bloodYour own family, whom you cannot disown.
“Whatever he has done he is still your flesh and blood.”
your flesh and blood is a phrase.
Practised in Idioms