Four is probably the toughest combination.  The best you can do is
still use triangles and leading lines.

            Dad>
                         <mom
child>
                 <infant

       Dad>
                    mom>
            infant
                              <child

If you have a properly "designed' portrait, where the client coordinates
clothing and the background compliments the outfits and 'key' of the image,
say a low key setting where the clothes and background are dark so the faces
are the lightest subjects, you can introduce a fifth element to give a
compositional balance.   Sometimes the easiest composition point is to
position a hand in a way that strikes the eye, say dad's hand on the kid's
knee.    A child can hold a large teddy bear.

Mom reads from a book with the kids looking at it, while dad looks at mom.
Dad fixes something, say a broken toy while mom combs the girl's hair.

a big bouquet of silk flowers on a tiny table stand.

if you are in their house then it should be easy to find something to put in
the background or foreground that becomes the 5th compositional element.

while most people are 'odds' there are a lot of folks who are evens, I'd say
about as many who are left handed, who knows.

I had an interesting conversation with a 'consulting' florist.  She says
that people have a preference to repeating patterns of 3's, 5's, 2's, 4's
and even noted one client with a distinct preference for 7's. (I thought
maybe that client just could afford more and wanted everybody to know it.)

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