I hope Im not being too harsh, but rule number 1 in portraits is make sure the face/faces can be seen.
In #1, the pole is strangely placed in the center between them, but even if you cant see them, the poses seem tense and awkward. Why are brother and sister kissing each other behind a pole anyway? Sorry, it just doesnt work at all for me. A pleasant kiss on the cheek where their faces are seen would be sweet.
In #2, its "blown out", not "blown up". The background is way too bright. You can tone that down by taking your aperature to about f/9 or more, so that it doesnt let as much light in the lens. Or you can position your subjects in a shady area, where there isnt so much hard sunlight.
Agree about #3, the double face doesnt work here.
Keep trying and glad you shared your work.