Cell Jr is similar to their father, except that they are small, because they have been born and because they are of colors blues(bruises). They do not possess the sting of their father, they cannot thus absorb the energy nor even to reproduce again.
They have similar skills in that of Cell, but they are widely lower in term of power. Nevertheless their level amounts to those of Vegeta and Trunks at this moment there of the history(story).