This expression means to bear a close resemblance. The phrase uses the verb 'to cast' in the sense of forming an object by running molten metal into a mould. The saying is quite old. It is known since the late sixteenth century.

Übersetzung:

aus dem gleichen Holz geschnitzt sein

Gegenteil(e)

The opposite of "to be cast in the same mould" is "to be as different as chalk and cheese".

Synonym(e):

You could also say: to be similar.