On GenoPro website (https://www.genopro.com/genogram/examples/) I see that in a lot of examples the parents and children are connected with two horizontal bars instead of one. How to get two? It seems, that adding a parent or adding a child always creates just one bar.

You can split a single family line (I think it looks untidy). Select the line and put the cusor over the central square. The cursor changes to a double arrow. Drag down to split the line.